Experimental Aspects of Platinum-Group Minerals

CHAPTER

EXPERIMENTAL ASPECTS OF PLATINUM-GROUP MINERALS

10

Anna Vymazalova´ 1 and Dmitriy A. Chareev2 1

Czech Geological Survey, Prague, Czech Republic 2Institute of Experimental Mineralogy RAS, Chernogolovka, Russia

CHAPTER OUTLINE 10.1 Introduction ............................................................................................................................... 304 10.2 Experimental Methods for Synthesis of Platinum-Group Minerals................................................... 314 10.3 Powder Samples ........................................................................................................................ 314 10.3.1 Dry Technique ...................................................................................................... 314 10.4 Single Crystals........................................................................................................................... 316 10.4.1 Congruent Techniques........................................................................................... 316 10.4.2 Incongruent Techniques ........................................................................................ 317 10.4.3 PGE-Bearing Crystals Prepared by Flux Technique ................................................... 320 10.5 Platinum-Group Minerals and Synthetic Analogues....................................................................... 324 10.5.1 Bortnikovite Pd4Cu3Zn........................................................................................ 326 10.5.2 Coldwellite Pd3Ag2S ........................................................................................... 327 10.5.3 Ferhodsite (Fe,Rh,Ni,Ir,Cu,Pt)9S8 ........................................................................ 328 10.5.4 Jacutingaite Pt2HgSe3 ........................................................................................ 328 ´ 10.5.5 Jagueite Cu2Pd3Se4............................................................................................ 329 10.5.6 Kalungaite PdAsSe ............................................................................................. 330 10.5.7 Kingstonite Rh3S4 .............................................................................................. 331 10.5.8 Kitagohaite Pt7Cu............................................................................................... 331 10.5.9 Kojonenite Pd7-xSnTe2 (0.3 # x # 0.8).............................................................. 332 10.5.10 Lisiguangite CuPtBiS3 ........................................................................................ 333 10.5.11 Lukkulaisvaaraite Pd14Ag2Te9.............................................................................. 334 10.5.12 Malyshevite PdCuBiS3 ........................................................................................ 335 10.5.13 Miessiite Pd11Te2Se2 .......................................................................................... 336 10.5.14 Milotaite PdSbSe ............................................................................................... 337 10.5.15 Naldrettite Pd2Sb............................................................................................... 338 10.5.16 Nielsenite PdCu3 ................................................................................................ 339 10.5.17 Norilskite (Pd,Ag)7Pb4 ........................................................................................ 340 10.5.18 Palladosilicide Pd2Si .......................................................................................... 341 10.5.19 Paˇsavaite Pd3Pb2Te2 .......................................................................................... 342 10.5.20 Skaergaardite PdCu ............................................................................................ 342 Processes and Ore Deposits of Ultramafic-Mafic Magmas through Space and Time. DOI: http://dx.doi.org/10.1016/B978-0-12-811159-8.00011-1 © 2018 Elsevier Inc. All rights reserved.

303

304

CHAPTER 10 EXPERIMENTAL ASPECTS OF PLATINUM-GROUP MINERALS

10.5.21 To¨rnroosite Pd11As2Te2 ....................................................................................... 343 10.5.22 Ungavaite Pd4Sb3 .............................................................................................. 344 10.5.23 Zaccariniite RhNiAs............................................................................................ 345 Acknowledgements ............................................................................................................................. 346 References ......................................................................................................................................... 346

10.1 INTRODUCTION The Platinum-group elements (PGEs) are of significant technological importance. PGEs are used primarily in industrial applications (e.g., catalysts) and have become widely established in chemical, electrical, and electronic engineering. The PGEs and the compounds they form have attracted considerable attention in recent years due to their specific properties and their application in new technologies. They exhibit various interesting physical, chemical, and structural properties that place these compounds at the interface of chemistry, mineralogy, solid-state physics, and material science. Therefore, there is still a demand for exploration and mining and to advance the understanding of the natural process that lead to their formation. This chapter consolidates the experimental methods that can be applied for the synthesis of PGE compounds. Dry synthesis and the major experimental methods used to try to obtain single crystals are summarized and some examples of the synthesis of PGE phases are discussed. A list of approved platinum-group minerals (PGMs) recognized up to the end of 2016, is presented with a focus on newly-named minerals and their experimental aspects. The up-to-date list of recognized PGMs is given in Tables 10.1
10.3. This chapter is written to encourage the application of experimental studies for a better understanding of PGM, their formation and occurrence under natural conditions. The available knowledge is often dispersed across the chemical, physical, mineralogical, and metallurgical literature. Additionally, there is often an information gap between investigations of synthetic systems and those of natural minerals. A number of PGE-bearing compounds have been determined and studied due to their specific (e.g., electrical or electrochemical) properties rather than their mineralogical significance. There is a wide range of data on the unary and binary systems available in the literature (e.g., a compendium of binary diagrams by Massalski, 1990). The systems containing PGEs were consolidated by Berlincourt et al. (1981), who thoroughly summarized the unary, binary, and ternary systems with PGEs. Later, Makovicky (2002) reported on further ternary and quaternary systems containing PGE. Since then, a few other ternary and quaternary systems of mineralogical significance containing PGEs were covered, involving Os, Pd, Pt, and Rh (Os-Mo-S: Dr´abek and Rieder, 2008; Pd-Ag-Te: Vymazalov´a et al., 2015; Pd-Ag-Se: Vymazalov´a et al., 2014b; Pd-Hg-Se: Dr´abek et al., 2014; Pd-Pb-Te: Vymazalov´a and Dr´abek, 2011; Pd-Sn-Te: Vymazalov´a and Dr´abek, 2010; Pd-Cu-Se: Makovicky and Karup-Møller, in press; Pd-Cu-Fe-S: Karup-Møller et al., 2008; Pd-NiFe-S: Makovicky and Karup-Møller, 2016; Pd-Pt-Sb: Kim, 2009; Pd-Pt-Ni-Te: Helmy et al., 2007; Pt-Hg-Se: Dr´abek et al., 2012; Rh-Cu-S: Karup-Møller and Makovicky, 2007). Nevertheless, as emphasized by Makovicky (2002) there is still a need to cover additional phase systems important for PGE deposits. Particularly unresearched are systems containing phases that are less common but of mineralogical significance and potentially of an economic importance (e.g., Pd-As-Sn,

Table 10.1 Platinum-Group Minerals (Ideal Formulas) Name Anduoite Arsenopalladinite Atheneite Atokite Borovskite Bortnikovitea Bowieite Braggite Cabriite Changchengite Chengdeite Cherepanovite Chrisstanleyite Coldwellitea Cooperite Crerarite Cuproiridsite Cuprorhodsite Damiaoite Daomanite Erlichmanite Ferhodsitea Ferronickelplatinum

Formula RuAs2 Pd8As2.5Sb0.5 Pd2As0.75Hg0.25 Pd3Sn Pd3SbTe4 Pd4Cu3Zn Rh2S3 (Pt,Pd)S Pd2SnCu IrBiS Ir3Fe RhAs Ag2Pd3Se4 Pd3Ag2S PtS (Pt,Pb)Bi3S42x CuIr2S4 CuRh2S4 PtIn2 PtCuAsS2 OsS2 (Fe,Rh,Ni,Ir,Cu,Pt)9S8 PtFe0.5Ni0.5

Name Ferrorhodsite Froodite Gaotaiite Genkinite Geversite Hexaferrum Hollingworthite Hongshiite Inaglyite Insizwaite Irarsite Iridarsenite Iridium Isoferroplatinum Isomertieite Jacutingaitea Jagu´eitea Kalungaitea Kashinite Keithconnite Kharaelakhite Kingstonitea Kitagohaitea

Formula FeRh2S4 PdBi2 Ir3Te8 (Pt,Pd)4Sb3 PtSb2 (Fe,Ru,Os,Ir) RhAsS PtCu Cu3PbIr8S16 PtBi2 IrAsS IrAs2 Ir Pt3Fe Pd11Sb2As2 Pt2HgSe3 Cu2Pd3Se4 PdAsSe Ir2S3 Pd20Te7 (Cu,Fe)4(Pt,Pb)4NiS8 Rh3S4 Pt7Cu

Name

Formula a

Kojonenite Konderite Kotulskite Kravtsovitea Laflammeite Laurite Lisiguangitea Luberoite Lukkulaisvaaraitea Majakite Malanite Malyshevitea Marathonitea Maslovite Mayingite Menshikovite Merenskyite Mertieite I Mertieite II Miessiitea Michenerite Milotaitea Moncheite

Pd72xSnTe2 Cu3PbRh8S16 PdTe PdAg2S Pd3Pb2S2 RuS2 CuPtBiS3 Pt5Se4 Pd14Ag2Te9 PdNiAs CuPt2S4 PdCuBiS3 Pd25Ge9 PtBiTe IrBiTe Pd3Ni2As3 PdTe2 Pd11(Sb,As)4 Pd8Sb2.5As0.5 Pd11Te2Se2 PdBiTe PdSbSe PtTe2 (Continued)

Table 10.1 Platinum-Group Minerals (Ideal Formulas) Continued Name a

Naldrettite Nielsenitea Niggliite Norilskitea Omeiite Oosterboschite Osarsite Osmium Oulankaite Padmaite Palarstanide Palladium Palladoarsenide Palladobismutharsenide Palladodymite Palladgermanidea Palladosilicidea Palladseite Paolovite Paˇsavaitea Platarsite Platinum Plumbopalladinite a

Formula

Name

Formula

Name

Formula

Pd2Sb PdCu3 PtSn (Pd,Ag)7Pb4 OsAs2 (Cu,Pd)7Se5 OsAsS Os Pd5Cu4SnTe2S2 PdBiSe Pd5(Sn,As)2 Pd Pd2As Pd2As0.8Bi0.2 (Pd,Rh)2As Pd2Ge Pd2Si Pd17Se15 Pd2Sn Pd3Pb2Te2 PtAsS Pt Pd3Pb2

Polarite Polkanovite Potarite Prassoite Rhodarsenide Rhodium Rhodplumsite Ruarsite Rustenburgite Ruthenarsenite Rutheniridosmine Ruthenium Shungfengite Skaergaarditea Sobolevskite Sopcheite Sperrylite Stannopalladinite Stibiopalladinite Stillwaterite Stumpflite Sudburyite Sudovikovite

PdBi Rh12As7 PdHg Rh17S15 (Rh,Pd)2As Rh Rh3Pb2S2 RuAsS Pt3Sn RuAs (Ir,Os,Ru) Ru IrTe2 PdCu PdBi Ag4Pd3Te4 PtAs2 Pd5Sn2Cu Pd51xSb22x Pd8As3 PtSb PdSb PtSe2

Taimyrite Tatyanaite Telargpalite Telluropalladinite Temagamite Testibiopalladite Tetraferroplatinum Tischendorfite Tolovkite To¨rnroositea Tulameenite Ungavaitea Urvantsevite Vasilite Verbeekite Vincentite Vymazalov´aitea Vysotskite Yixunite Zaccariniitea Zvyagintsevite

(Pd,Cu)3Sn Pt9Cu3Sn4 Pd22xAg11xTe Pd9Te4 Pd3HgTe3 PdSbTe PtFe Pd8Hg3Se9 IrSbS Pd11As2Te2 PtFe0.5Cu0.5 Pd4Sb3 Pd(Bi,Pb)2 Pd16S7 PdSe2 (Pd,Pt)3(As.Sb,Te) Pd3Bi2S2 PdS Pt3In RhNiAs Pd3Pb

New minerals described from 2002 to 2016.

Table 10.2 Revised Platinum-Group Minerals, Crystallographic Data Mineral

Crystallographic Data

Unit Cell Parametrs ˚) a (A

˚) b (A

˚) c (A

Reference 

β( )

˚ 3) V(A

Z

114.996

140.26 337.3 2106.1

3 2 12

Name

Formula

Space group

Atheneite Chrisstanleyite Mertieite II

Pd2As0.75Hg0.25 Ag2Pd3Se4 Pd8Sb2.5As0.5

Hexagonal Monoclinic Trigonal

P6/2m P21/c R3ch

6.813 5.676 7.5172

10.342

3.4892 6.341 43.037

Sopcheite

Ag4Pd3Te4

Orthorhombic

Cmca

12.212

6.138

12.234

917.1

4

Temagamitea Tischendorfitea

Pd3HgTe3 Pd8Hg3Se9

Hexagonal Orthorhombic

P3m1 Pmmm

7.8211 7.1886

16.8083

17.281 6.4762

917.8 782.51

6 2

a

Crystal structure solved from the synthetic analogue.

Bindi (2010) Topa et al. (2006) Karimova et al. (in press) Laufek et al. (in press) Laufek et al. (2016) Laufek et al. (2014)

Table 10.3 Platinum-Group Minerals, Described Since 2002 and Their Crystallographic Data Crystal Structure Data

Mineral

Space Group

Unit Cell Parametrs ˚) a (A

Name

Formula

Bortnikovite

Pd4Cu3Zn

Tetragonal

Coldwellite

Pd3Ag2S

Cubic

Ferhodsite

Tetragonal

Jacutingaite

(Fe,Rh,Ni, Ir,Cu,Pt)9S8 Pt2HgSe3

Jagu´eite

Cu2Pd3Se4

Kalungaite

PdAsSe

Kingstonite

Rh3S4

Monoclinic

C2/m

10.4616

Kitagohaite Kojonenite

Pt7Cu Pd7-xSnTe2

Cubic Tetragonal

7.7891 4.001

Kravtsovite

PdAg2S

Orthorhombic

Fm3m I4/ mmm Cmcm

7.9835

Lisiguangite Lukkulaisvaaraite

CuPtBiS3 Pd14Ag2Te9

Orthorhombic Tetragonal

P212121 I4/m

Malyshevite

PdCuBiS3

Orthorhombic

Marathonite

Pd25Ge9

Miessiite

Pd11Te2Se2

Milotaite Naldrettite

PdSbSe Pd2Sb

˚) b (A

Reference β ( )

Z

306.0

3

380.61

4

7.2470

?

10.009

9.840

985.77

Trigonal

P3m1

7.3477

5.2955

247.59

2

Monoclinic

P21/c

5.672

318.1

2

Pa3

6.089

225.78

4

666.34

6

20.929

472.57 335.0

4 2

5.9265

5.7451

271.82

4

7.7152 8.9599

12.838

4.9248 11.822

487.80 949.1

4 2

Pnam

7.541

6.4823

11.522

563.204

4

P3

7.391

10.477

495.65

1

Cubic

Fd3m

12.448

1929.0

8

Cubic Orthorhombic

P213 Cmc21

6.3181 3.3906

252.20 414.097

4 8

Trigonal

8.50

˚ 3) V (A

P4/ mmm ? P4332

Cubic

6.00

˚) c (A

9.910

10.7527

17.5551

6.264

6.2648

6.957

115.40

109.0

Mochalov et al. (2007) McDonald et al. (2015) Begizov (2009)a Vymazalov´a et al. (2012a) Paar et al. (2004), Topa et al. (2006) Botelho et al. (2006) Stanley et al. (2005) Cabral et al. (2014) Stanley and Vymazalov´a (2015) Vymazalov´a et al. (in press) Yu et al. (2009) Vymazalov´a et al. (2014a) Chernikov et al. (2006) McDonald et al. (2016) Kojonen et al. (2007) Paar et al. (2005) Cabri et al. (2005)

Nielsenite

PdCu3

Tetragonal

P4mm

3.7125

25.62

353.2

4

Norilskite Palladogermanide

(Pd, Ag)7Pb4 Pd2Ge

Trigonal

P3121

8.9656

17.2801

1202.92

6

Hexagonal

P62m

6.712

3.408

132.96

3

Palladosilicide Paˇsavaite

Pd2Si Pd3Pb2Te2

Hexagonal Orthorhombic

P62m Pmmn

6.496 8.599

3.433 6.3173

125.5 322.6

3 2

Skaergaardite

PdCu

Cubic

Pm3m

3.0014

27.0378

1

To¨rnroosite

Pd11As2Te2

Cubic

Fd3m

12.3530

1885.03

8

Ungavaite

Pd4Sb3

?

7.7388

1446.02

8

Vymazalov´aite

Pd3Bi2S2

Cubic

I213

8.3097

573.79

4

Zaccariniite

RhNiAs

Tetragonal

P4/ nmm

3.5498

77.59

2

a

No further data available.

Tetragonal

5.9381

24.145

6.1573

McDonald et al. (2008) Vymazalov´a et al. (2017) McDonald et al. (2017b) Cabri et al. (2015) Vymazalov´a et al. (2009) Rudashevsky et al. (2004) Kojonen et al. (2011) McDonald et al. (2005) Sluzhenikin et al. (in press) Vymazalov´a et al. (2012b)

Table 10.4 Experimental Data for Ternary Systems and the Corresponding PGM (Ideal Formulae) System

Mineral Name

Formula

Ir-As-S Ir-Bi-S Ir-Bi-Te Ir-Cu-S Ir-Sb-S Os-As-S Pd-Ag-Pb

Irarsite Changchengite Mayingite Cuproiridsite Tolovkite Osarsite Norilskite

IrAsS IrBiS IrBiTe CuIr2S4 IrSbS OsAsS (Pd,Ag)7Pb4

Pd-Ag-S

Coldwellite

Pd3Ag2S

Kravtsovite

PdAg2S

Pd-Ag-Se

Chrisstanleyite

Ag2Pd3Se4

Pd-Ag-Te

Lukkulaisvaaraite

Pd14Ag2Te9

Pd-As-Bi

Sopcheite Telargpalite Palladobismutharsenide

Ag4Pd3Te4 Pd2-xAg11xTe Pd2As0.8Bi0.2

Type of Diagram, at T ( C) None None None None None None Isothermal section, 400 Isothermal section, 400, 550 Vertical section, 400
1600 Isothermal section, 350, 430, 530 Isothermal section, 350, 450 Vertical section, 0
1000 Isothermal section, 400 480

Pd-As-Hg Pd-As-Sb

Pd-As-Se

Atheneite Arsenopalladinite Isomertieite Mertieite I Mertieite II Kalungaite

Pd2As0.75Hg0.25 Pd8As2.5Sb0.5 Pd11Sb2As2 Pd11(Sb,As)4 Pd8Sb2.5As0.5 PdAsSe

None Isothermal section, 710

None

Compositional Range

Reference

Full

Sarah et al. (1981) Vymazalov´a et al., in prep. Raub (1954)

Full Partial, Ag2S-Pd Full Full Partial, Ag22.2Pd66.6 Te11.2-Ag66.7Te33.3

Vymazalov´a et al. (2014b) Vymazalov´a et al. (2015) Chernyaev et al. (1968)

Partial, As-Bi-Bi50Pd50As15Bi35Pd50-As33Pd67-As25Pd75Bi25Pd75-Pd Partial, Pd1.97As0.80Bi0.23Pd2As

El-Boragy and Schubert (1971a)

Partial, PdAs2-Pd73As27-Pd72Sb28Pd38Sb62

Cabri et al. (1975)

Cabri et al. (1976)

Pd-As-Sn

Palarstanide

Pd5(Sn,As)2

Pd-As-Te

To¨rnroosite

Pd11As2Te2

Pd-Bi-Pb

Urvantsevite

Pd(Bi,Pb)2

Pd-Bi-S Pd-Bi-Se Pd-Bi-Te

Vymazalov´aite Padmaite Michenerite

Pd3Bi2S2 PdBiSe PdBiTe

Pd-Cu-Se

Jagu´eite Oosterboschite

Cu2Pd3Se4 (Cu,Pd)7Se5

Pd-Cu-Sn

Cabriite Stannopalladinite Taimyrite Bortnikovite

Pd2SnCu Pd5Sn2Cu (Pd,Cu)3Sn Pd4Cu3Zn

Pd-Cu-Zn

Pd-Hg-Se

Tischendorfite

Pd8Hg3Se9

Pd-Hg-Te Pd-Ni-As

Temagamite Majakite

Pd3HgTe3 PdNiAs

Tentative isothermal section, 500 Isothermal section, 25 Isothermal section, 480 Vertical section, 180
600 None None Isothermal section, 480 Isothermal section, 480 Isothermal section, 300, 400, 550, 650

Partial

Pratt (1994)

Partial, SnAs-Pd50Sn50-Sn Full Partial,PdBi2-PdPb2

Partial, Pd-rich corner Partial, Te-Bi4Te3-Bi60Pd40-PdTe Full

None

System studied in hydrothermal chloride solutions (Pd-Sn-Cu-HCl) at 300 and 400  C

Tentative isothermal section, 800

Partial

Experimental points at 350 to 800 Isothermal section, 430 Isothermal section, 400 None Isothermal section, 450

Partial

Partial, Pd-Cu region containing up to 5 at.% Zn Full None Partial

El-Boragy and Schubert (1971b) Zhuravlev (1976)

El-Boragy and Schubert (1971b) Hoffman and MacLean (1976) Makovicky and Karup-Møller (in press) Evstigneeva and Nekrasov (1980) Lebrun et al. (2007) based on data from Dobersek and Kosovinc (1989) Dobersek and Kosovinc (1989) Schubert et al. (1955) Dr´abek et al. (2014) Gervilla et al. (1994) (Continued)

Table 10.4 Experimental Data for Ternary Systems and the Corresponding PGM (Ideal Formulae) Continued System

Mineral Name Menshikovite

Pd-Pb-Te

Pd-Pb-S Pd-Sb-Se Pd-Sb-Te

Paˇsavaite

Laflammeite Milotaite Borovskite

Testibiopalladite

Formula Pd3Ni2As3

Pd3Pb2Te2

Pd3Pb2S2 PdSbSe Pd3SbTe4

PdSbTe

Pd-Sn-Te

Kojonenite

Pd7-xSnTe2

Pd-Te-Se Rh-Pd-As

Miessiite Rhodarsenide Palladodymite

Pd11Te2Se2 (Rh,Pd)2As (Pd,Rh)2As

Pt-As-S

Platarsite

PtAsS

Pt-Bi-Te Pt-Cu-Fe

Maslovite Tulameenite

PtBiTe PtFe0.5Cu0.5

Pt-Cu-S

Malanite

CuPt2S4

Type of Diagram, at T ( C) Isothermal section, 790 Isothermal section, 500 Isothermal section, 400 Isothermal section, 480 None None Isothermal section, 400 Isothermal section, 600 Isothermal section, 800 Isothermal section, 1000 Isothermal section, 400 None Tentative isothermal section, 750

Isothermal section, 1000 None Isothermal section, 600, 1000 None

Compositional Range

Reference

Full Partial, NiAs2-Ni5As2-Pd5As2PdAs2 Partial Pd3Pb-Pb-Te-PdTe Partial, Pd-rich corner

Full Full

El-Boragy et al. (1984) Vymazalov´a and Dr´abek (2011) El-Boragy and Schubert (1971b)

El-Boragy and Schubert (1971b) Kim and Chao (1991)

Partial, Pd-Pd40Sb60-Pd40Te60 Partial, Pd60Sb40-Pd-Pd60Te40 Full

Vymazalov´a and Dr´abek (2010)

Partial, As-PdAs2-RhAs2

Pratt (1994) based on data from Bennett and Heyding (1966) Skinner et al. (1976)

Full composition

Full composition

Shahmiri et al. (1985)

Pt-Cu-Sn Pt-Fe-Ni Pt-Hg-Se

Tatyanaite Ferronickelplatinum Jacutingaite

Pt9Cu3Sn4 PtFe0.5Ni0.5 Pt2HgSe3

Pt-Pd-S

Braggite

(Pt,Pd)S

Pt-Pd-Sb

Genkinite

(Pt,Pd)4Sb3

Rh-As-Ni Rh-As-S Rh-Cu-S

Rh-Fe-S

Rh-Pb-S Ru-As-S

Zaccariniite Hollingworthite Cuprorhodsite

Ferrorhodsite

Rhodplumsite Ruarsite

RhNiAs RhAsS CuRh2S4

FeRh2S4

Rh3Pb2S2 RuAsS

None None Isothermal section, 400 Isothermal section, 800, 1000 Isothermal section, 1000 Isothermal section, 600 Isothermal section, 800, 1000 Isothermal section, 1000 None None Isothermal section, 500, 700, 900 Isothermal section, 540 Isothermal section, 500, 900 Vertical section 900
1500 Vertical section 1050
1350 Liquidus projection None None

Full composition Partial composition; Pd-Pt-PtSPdS Full composition Partial composition; Pd72Sb28Pt84Sb16-Sb Full composition

Dr´abek et al. (2012) Cabri et al. (1978) Skinner et al. (1976) Kim and Chao (1996)

Full

Kim (2009)

Full

Karup-Møller and Makovicky (2007)

Partial, Cu2-xS-Rh17S15-RhS3CuxRhS31x-Cu2-xS Full composition Partial composition; FeS1.09-FeRh Partial composition; FeS1.09Rh2S3 Partial composition; Rh-Rh40S60Fe48S52-Fe

Makovicky et al. (2002) Bryukvin et al. (1990)

314

CHAPTER 10 EXPERIMENTAL ASPECTS OF PLATINUM-GROUP MINERALS

Pd-As-Sb, Pd-As-Hg, Pd-Cu-Sn, Pt-Cu-Sn, Pt-Bi-Te). We summarize the ternary PGM (taking into the account the ideal composition of minerals) and corresponding systems, and refer to data on phase diagrams in the literature (Table 10.4). There are still a large number of systems containing PGE-bearing ternary minerals without a knowledge of ternary phase diagrams and phase relations. As shown in Table 10.4, there is still not enough knowledge on several complete isothermal sections and very few systems have been studied at more than one temperature. Furthermore, some ternary systems also require re-investigation due to new observations within the corresponding binary systems and by the discovery of new minerals.

10.2 EXPERIMENTAL METHODS FOR SYNTHESIS OF PLATINUM-GROUP MINERALS Experimental studies have various implications for geological processes. One of the aims of experimental synthesis is to determine phase relations under specific conditions with a view to understanding natural processes. The knowledge of phase relations allows prediction of the mineral assemblages stable at natural conditions. Experimental study of thermal stabilities and the solid solutions of PGM help to understand their formation, occurrence, and accumulation in nature, thus are directly applicable to the study of mineral deposits. The other aim of experimental synthesis of PGE compounds is to obtain single crystals of sufficient size for detailed investigations. Single crystals can be studied in terms of crystal structure determination that is also applicable to the mineralogy of PGM. The knowledge of crystal structures and structural mechanisms of various substitutions within PGM also have implications in mineral processing and geo-metallurgy. Various PGE compounds are also of materials science interest and have industrial applications whereby PGE phases are studied in terms of specific properties (e.g., chemical, electrical, optical, magnetic, semiconductor, etc.). We describe the preparation methods that can be used for PGE phases and minerals synthesis. In the first part (Section 10.3) we focus on methods resulting in powder products and in the second part (Section 10.4) we discuss suitable methods for producing single crystals. We also provide some examples of crystal growth and synthesis conditions for various PGE phases and minerals that might be applicable for preparation of other PGE compounds.

10.3 POWDER SAMPLES 10.3.1 DRY TECHNIQUE The silica-glass tube method belongs to the classical experimental methods, so-called dry technique or solid phase synthesis. The method has been described in detail by Kullerud (1971), focusing on sulfide synthesis. The silica tube method is suitable for synthesis of PGE sulfides, selenides, and tellurides, as well as for other compounds and alloys that are formed at temperatures below 1300 C (when silica starts to recrystallize and may become permeable). Charges are carefully weighed out from the pure elements

10.3 POWDER SAMPLES

315

and placed into the silica-glass tube. The starting materials are either pure elements or presynthesized phases, or combinations. To prevent loss of material to the vapor phase during experiments, the free space in the tubes is reduced by placing closely fitting glass rods over the charge. The charges should be as small as possible, but still having the sufficient material for the product investigation (e.g., polished section, X-ray diffraction). Smaller quantities are easier to homogenize, and another consideration is the high prices of pure platinum-group-element starting reagents. The tubes with the charge are evacuated and subsequently sealed in, e.g., a hydrogen-oxygen flame. The capsules with the charge are then heated in horizontal or vertical furnaces, which allow faster quenches. In order to ensure the homogeneity, the samples are after the first melting/heating opened and the products are finely reground under acetone in an agate mortar. In some cases, the reground samples are pelletized under pressure before being reinserted in silica tubes, evacuated and reheated (e.g., Cabri, 1973; Cabri et al., 1976 (palladobismutharsenide)). In many cases the samples are reground several times during the heating before the equilibrium is attained. Reactions in silica tubes rely on diffusion and can be exceedingly slow, particularly for PGE-rich phases and for phase studies at low temperatures. Therefore, some experiments require long term heating to reach the equilibrium that may take from several months up to a year. After heating the experimental runs are quenched by dropping the capsule in cold water. In order to obtain sulfides with high sulfur content (e.g., PtS2), a long silica tube located in a temperature gradient (Pt in a hot and S in a cold zone) can be used to prevent the explosion of the tube that might be caused by the high sulfur vapor pressure. The run products are suitable for powder X-ray diffraction analyses, and are usually examined in polished sections using reflected light microscopy, electron-scanning microscopy and electronmicroprobe techniques. In most cases, the run products are very fine grained and required detailed and precise examination (Fig. 10.1A,B).

FIGURE 10.1 Back-scattered electron images of experimental products obtained by the dry technique: (A) synthetic jacutingaite (Pt2HgSe3) in association with sudovikovite (PtSe2), a quench from 400 C (heated for 71 days); (B) fine grained intergrowths of lukkulaisvaaraite (Pd14Ag2Te9) with telargpalite (Pd2-xAg11xTe) and hessite (Ag2Te), a quench from 350 C (heated for 130 days).

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10.4 SINGLE CRYSTALS Single crystals of PGE phases and minerals are required for crystal structure investigations and for more accurate determination of their properties. In some cases, phase associations obtained in the form of sufficiently large coexisting crystals help the study of phase relations. Crystal growth techniques can in general be divided into congruent and incongruent. Congruent techniques constitute crystal growth from the melt of the desired substance (melt of a similar composition) and are characterized by a L-S phase reaction. Incongruent techniques are based on crystal precipitation from liquid or gas solvents. The principal methods are vapor transport, hydrothermal (water solution) and flux techniques. Moreover, techniques can be distinguished based on spontaneous crystallization (when crystals are formed via nucleation) or controlled crystallization (with seed crystals). The silica-glass tube method (dry technique or so-called solid phase synthesis technique) described in Section 10.3 also allows the preparation of micrometer-size crystals.

10.4.1 CONGRUENT TECHNIQUES There are various congruent techniques for crystal preparation (e.g., Wilke, 1973), and all of them are based on a gradual removal of heat from the liquid-solid boundary; they differ in the way this boundary is shifted. An advantage of incongruent techniques is the possibility of synthesizing incongruently melting crystals and synthesis at lower temperatures. The Bridgman
Stockbarger technique (or Bridgman technique, Bridgman, 1925) is usually performed in a vertical reaction vessel with a cone-shaped bottom. The vessel with the melt is slowly moved down to the gradient tube furnace, where the temperature in its lower part is lower than in its upper part. Crystallization starts from the bottom of the vessel. The cone shape of the bottom ensures the formation of a single nucleus rather than several. Sometimes a process in which the reaction vessel is cooled in the temperature gradient without moving along the gradient furnace is also called the Bridgman technique. The Czochralski technique (Czochralski, 1918) is implemented by gradually pulling the cooled seed crystal above the free surface of the melt. The Kyropoulos technique (Kyropoulos, 1926) is similar but differs in that there is no mechanical movement of the seed crystal. The temperature of the melt is slowly decreased so that the crystal gradually grows on the seed forming a half-sphere. Crystal growth via the Verneuil technique is implemented by gradually adding melt droplets to the surface of the growing crystal. The Pfann technique or zone melting constitutes melting by a movable circular heater of a powder-like starting mixture, which usually is compressed into a cylinderical shape (Pfann, 1966). Phases suitable for growing crystals from their melt can be identified from the corresponding known phase diagrams by having a common liquidus and solidus maximum. For example, in the system Pd-Te: the phases Pd8Te3, PdTe (kotulskite) and PdTe2 (merenskyite) display this property. Most of the congruently melting crystals of chalcogenides and pnictogenides are grown using the Bridgman
Stockbarger technique. For example, crystals of PdTe2, up to 7 3 16 mm in size, were grown using this method by Lyons et al. (1976). The growth was carried out in a silica-glass reaction vessel, which was moved down at 2.8 mm/hour inside a gradient furnace with the temperature of the hot zone at 800 C. Apparently, crystals of other congruently melting phases can be prepared

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using a similar technique: PtAs2 (sperrylite), PdBi (polarite), Pd3Pb (zvyagintsevite), PdSb (sudburyite), Pd2Si (palladosilicide), PtSb2 (geversite), Pt3Sn (rustenburgite), PtSn (niggliite), Rh2Se3 (bowieite), PtSe2 (sudovikovite), PtTe2 (moncheite), and others. Congruent techniques are mainly used to grow single phase samples at temperatures near the liquidus and therefore in general are not suitable for studies of phase relations.

10.4.2 INCONGRUENT TECHNIQUES 10.4.2.1 Vapor Transport Technique In the vapor-transport crystal-growth technique (Schafer, 1962), a solid substance interacts with a transport agent via a reversible chemical reaction, forming only gas products which flow to another part of the reaction system with different physical and chemical conditions, where the initial substance is formed again but in a single-crystal state. The main requirements for the transport are a concentration gradient and a reversible transport reaction. Usually the transport agents are halogens or their compounds (e.g., ICl3, AlCl3, S2Cl2). The transport of transition elements (PGE and Fe, Ni, Co) can be facilitated by phosphorus, oxygen, hydrogen and, consequently, water. The vapor transport process is similar to sublimation but it can occur at lower temperatures. To describe the temperature profile of the transport it is convenient to use the T1-T2 notation where T1 is the temperature of the charge and T2 is the temperature of the growth zone. Crystal growth is usually performed in closed cylindrical reaction vessels made of silica or ordinary glass. A part of the charge (the solid substance) with the transport agent is placed at one end of the vessel. Usually the quantity of the transport agent is orders of magnitude less than that of the charge. In order to create different temperatures at the two ends of the vessel, gradient furnaces or a natural temperature gradient are used. Cylindrical silica ampoules can be used in the vapor transport technique if the hot end of the ampoule is at a temperature not higher than 1000
1200 C. At higher temperatures silica-glass softens, recrystallizes or reacts with a charge, and silica becomes permeable to gas(es). If the hot end of the ampoule has to be at a temperature greater than 1300 C, a white-hot wire is soldered into the ampoule. Campbell et al. (1949) described transport of various metals including iridium, osmium, platinum, rhodium, and ruthenium using CO and halogens as transport agents. The formation of platinum whiskers by decomposition of platinum chloride at 800 C was described by Brenner (1956). Schafer (1962) results in the formation of iridium (1325-1130 C) and platinum crystals (temperature in the hot end 5 1500 C) using oxygen as a transport agent. At similar or lower temperatures, in a flow of oxygen, crystals of PGE oxides such as: OsO2 (Rogers et al., 1969; Yen et al., 2004), RuO2, and IrO2 (Rogers et al., 1969; Horkans and Shafer, 1977) or Ru1-xIrxO2 (Georg et al., 1982) can be also grown. Tiny crystals of osmium phosphide OsP2 were grown at 1000 C using iodine (Bugaris et al., 2014) and crystals of palladium arsenides (Pd3As and Pd5As) were grown at 500
600 C using chlorine by Saini et al. (1964) who noted that the transport does not occur with other halogens. Crystals of chalcogenides are usually prepared using halogens. Crystals of RuS2 and RuSe2 were prepared following such an approach by, e.g., Bichsel et al. (1984), Vaterlaus et al. (1985), Fiechter and Ku¨hne (1987). The growth of RuS2 occurred in the temperature profile 1040-1020 C using a mixture of ICl3 and S2Cl2 as transport agents with an excess of sulfur. As a result, crystals

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4 3 4 3 4 mm in size were obtained in about 30 days. The growth of RuSe2 occurred at 1100-1070 C using ICl3; the charge also contained an excess of the chalcogen, and as a result 10 3 8 3 5 mm crystals were grown. Crystals of RuTe2 were grown using ICl3 at 1060-960 C over a period of 10 days (Huang et al., 1994) and Colell et al. (1994) synthesized RuS2 crystals containing up to 50 at.% Ir (temperature profile 1100-1050 C) using iodine. Similarly, Tsay et al. (1994) grew iron-doped RuS2 crystals using ICl3. Crystals of Rh2S3 were synthesized within a temperature profile from 1000-1020 C using bromine (Parthe et al., 1967). Crystals of PtS2 were grown using a mixture of chlorine and phosphorus (Finley et al., 1974). The charge contained platinum, sulfur, and phosphorus with molar ratios 1:3:1. Chlorine was added in order to create a pressure of 10,000 Pa. The ideal temperature profile was from 800-740 C, under which flat hexagonal crystals with sizes up to 5 3 5 mm were grown after 6 days. At lower temperatures (700-670 C) the transport was insignificant and at higher temperatures (900-840 C) the two-phase association PtS 1 PtS2 was obtained. Crystals of Pt(S,Se)2, with varying S/Se ratios, in association with crystals of PtTe2, were prepared with phosphorus as the major transport agent, sometimes with addition of chlorine, with temperatures of 850
875 C at the hot end and 750
690 C in the cold end (Soled et al., 1975, 1976).

10.4.2.2 Hydrothermal Techniques Solution and hydrothermal techniques are based on recrystallization of the substance in aqueous solutions at room or higher temperature. At low temperatures, unlike in the vapor transport technique, supersaturation can be reached by gradual evaporation of the water solution; by addition of compounds that lower the solubility of the desired phase (e.g., pH variation); by mixing solutions containing the components of the substance crystallized; electrolysis; transport reactions; and substance exchange on the boundary of two phases. The gradual temperature increase causes an increase in the solubility of most chemical compounds, reaction rates, and diffusion rates. However, the synthesis needs to be done in durable hermetic vessels (autoclaves) at temperatures above 100 C. Usually transport is driven by a temperature gradient and the migration of the phase(s) occur(s) mostly via convection. Often, in order to increase the solubility of the charge, a mineralizer (e.g., KClO3), which is similar to the transport agent in the vapor transport technique, is added to water. Mineralizers do not form separate phases. The transport of chalcogenides can be increased by adding acid or NH4I to the water, as chalcogenides decompose in alkali solutions. Iodides (e.g., NH4I) are the most preferable halogenides because iodine and sulfide ions have the largest difference in ionic radius, which prevents iodine from substituting into the lattice of the growing sulfide. Most often autoclaves made of stainless steel or titanium alloys are used as laboratory vessels for hydrothermal synthesis, and allow for operating at temperatures up to B500 C and pressures up to 2000 atmospheres. The solution is often placed in a Teflon or a noble metal liner to protect the autoclave. Hermetic ampoules made of noble metals or silica glass, and of a size less than the internal volume of the autoclave, can be also used to protect from an aggressive environment. Free external space in this case is filled with water. When soft metal ampoules are used, the water often serves as the pressure medium. Ampoules made of noble metals in some cases are the source of the noble metal. When silica ampoules are used, the external water creates a counterpressure that protects the silica ampoule from destruction. Gas, e.g., CO2 (Rau and Rabenau, 1968) also can be used as the external medium.

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Crystals of various metals including platinum were grown hydrothermally by, e.g., Rau and Rabenau (1968). The crystal growth was carried out in silica ampoules in concentrated aqueous solutions of HCl, HBr, or HI in a temperature gradient (with a hot end 420
600 C). To prevent the ampoules from cracking they were placed in autoclaves together with dry carbon dioxide which created the counter-pressure by evaporation. It was also shown that the addition of oxidizers, e.g., Cl2, Br2, H2O2 or residual oxygen boosts the metal transport due to the increase in concentration of metal ions dissolved in water. Schwartz et al. (1982) prepared platinum oxide crystals (β-PtO2) in equilibrium with other compounds (e.g., CdPt3O6) in sealed platinum ampoules in KClO3 solution by cooling the solution. Crystals of Rh2S3 and Rh17S15 with sizes up to a hundred microns were prepared by, e.g., Zhang et al. (2009), using rhodium carbonyl Rh6(CO)16 and crystals of sulfur as starting chemicals, grown in Teflon-lined autoclaves at 200
400 C. The hydrothermal technique is less commonly used to grow PGE-bearing crystals. However, it has been used to study the conditions of formations as in, e.g., the Pd-Sn-Cu-HCl system by Evstigneeva and Nekrasov (1980).

10.4.2.3 Flux Technique The flux technique (e.g., Wilke, 1973) is based on the gradual cooling of a multicomponent system. The solubility of the components in the melt decreases with decreasing temperature and this leads to the formation of crystals of certain compounds. Due to the complexity of a multicomponent system the composition of the grown crystals differs from that of the melt. The flux technique is somewhat intermediate between hydrothermal (incongruent) and congruent techniques. The major advantage of the flux technique, in comparison with the hydrothermal technique, is the broad range of temperatures (from 25 C to 1500 C) that can be used for synthesis. The other advantage is the large variety of possible solvents, e.g., various combinations of oxides, salts, hydroxides, and other heteropolar compounds that can be used. Metals with low melting temperature such as Sn, Pb, Bi, Te, In, Hg, eutectic mixtures of lead fluoride or lead oxide, tungsten, molybdenum oxides, or metal halides or alkali metal poly-chalcogenides (e.g., Na2Sn) are often used as solvents. In general, the flux method is not very complicated. Specific amounts of the charge and the solvent, in powder form, are placed in a crucible made of inert material. Usually the crucible is tightly closed with a lid to reduce evaporation of the solvent. Then during the shortest possible period of time (several hours) the crucible is heated up to the maximum point. After this, the temperature is quickly decreased by 50
100 C to create a supersaturation or to form nuclei of the desired compound, and then the temperature is slowly decreased at 3
5 C per hour. Afterwards, at a certain temperature the experimental product is quenched or the melt is mechanically separated from the crystals (decanted). In some cases, the crucible with the charge is not quenched or cooled to the room temperature because the desired phase can precipitate as crystals only within a certain temperature interval. In some cases, more complicated cooling modes are used, such as oscillations in the area where crystallization starts. Crucibles used for crystal growth are made most often from precious metals, corundum, or silica-glass tubes. However, as described for dry synthesis in Section 10.3, the silica-glass softens at temperatures over 1300 C and dissolves at temperatures over 600 C in PbF2-PbO melts. The flux method is quite universal; crystallization may be possible in poorly concentrated solutions as well as in highly concentrated solutions for a single-component composition, almost in the field of crystallization from the melt. When the solution of a desired material shows a low degree

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of concentration then the method displays similarities with the hydrothermal or vapor-transport techniques. In cases where the composition of the solution is almost identical with the crystallized substances then the flux method is similar to synthesis from the melt of the desired compound, like the Bridgman or Czochralski techniques. Usually the term “flux technique” is used when the amount of compound being crystallized is more than 6%
8% of the total liquid phase. However, the self-flux technique can be also distinguished when the composition of an initial melt is the same as that of the resulting crystals. Supersaturation is most commonly created by a slow cooling or by gradual evaporation of the solvent. In some cases, small crystals are obtained under isothermal conditions.

10.4.3 PGE-BEARING CRYSTALS PREPARED BY FLUX TECHNIQUE The first crystals of PGE compounds using the flux technique were obtained in the 19th century (e.g., Rossler, 1895; as summarized in Chirvinskii, 1995). For example, dendritic crystals of gold and platinum were prepared by melting Au/Pt with NaCl, Na2S2O7 or Fe2(SO4)3, PtAs2 (sperrylite), PtSb2 (geversite) and PtBi2 (insizwaite) crystals in lead flux, and crystals of RuS2 (laurite) and PtS2 by melting Ru (or Pt) in iron sulfide and borax together at B900 C. Crystals of PGE compounds can be grown in various solvents by gradually decreasing temperature. Reviews by Fisk and Remeika (1989) and Canfield and Fisk (1992) summarize the application of low-temperature melting metals to prepare crystals by the flux method for many chemical compounds including PGE-bearing phases. The growth of UPt3, NpPt3, PtMnSb, and UIr3 crystals in bismuth, RRh4B4, RIr2, and UIr3 in copper, RPt2 and YbPtx in lead, and R3Rh4Sn13 in tin (where R is a rare-earth element) was shown by Fisk and Remeika (1989). Further, crystals of UPt3, YPd, RBiPt, and R3Bi4Pt3 prepared in bismuth; R2Pt4Ga8 in gallium, LaPbPt, CePbPt, LaBiPt, CeBiPt, and PrBiPt in lead, and U3Sb4Pt3 and PtSb2 in antimony are summarized in Canfield and Fisk (1992). Melts of Al, Ce, Fe, In, Hg, Zn, and Ag can be used to prepare PGE-bearing crystals. Here we provide some examples for crystal growth of PGE-bearing phases and minerals and discuss the experimental conditions. Crystals of PGE with P, As, Sb, Bi (pnictides) phases can also be prepared by cooling the metal melts. For example, crystals of RhP3 were grown in tin flux (Odile et al., 1978); the synthesis was done in silica-glass tubes, where tin formed about 85% of the total volume of the charge. Tubes with the charge were heated to 1150 C for some hours, until complete dissolution. Afterwards, the tube with the charge was cooled to 550 C at a rate of 5 C per hour and the experimental products were washed from tin in hydrochloric acid. Similarly, by cooling the tin melt, other PGE-bearing phosphides can be synthesized, as PtP2, RuP2, IrP2, RuP4, and OsP4 (Baghdadi et al., 1974; Kaner et al., 1977 Ruehl and Jeitschko, 1982), OsP2 and OsAs2 or OsSb2, in an excess of antimony (Bugaris et al., 2014). Savilov et al. (2005) prepared the ternary phase Pd7-xSnTe2, an analogue of kojonenite, using a tin flux. Ternary PGE arsenides can be also synthesized in a metal flux. For example, crystals of BaRh2As2 were grown in a lead flux (Singh et al., 2008) with an initial mixture of Ba1.1Rh2As2.1Pb50. Due to the presence of barium the synthesis was performed in a glass made of Al2O3, sealed in an evacuated silica-glass tube. The mixture was cooled from 1000 C to 500 C at a rate of 5 C per hour. As a result, crystals 1.5 3 1.5 3 0.1 mm3 in size were obtained. The authors did not mention if lead was present in the resulting crystals.

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Further, the flux technique can be applied for PGE oxides. For example, needle-like crystals of CaIrO3 were grown in platinum crucibles with CaCl2 1 Ca(OH)2 1 Ir melt (in molar ratio 10:1:1) by cooling from 827 to 327 C at a cooling rate of 10 C per hour (Sugahara et al., 2008). The flux method can be also used for crystal growth of PGE chalcogenides. For example, crystals of CuIr2S4 were grown by cooling a bismuth-based melt (Matsumoto and Nagata, 2000) from an initial temperature of 1100
1000 C to a final temperature of 500 C. The bismuth melt was decanted and the remaining crystals were washed from the residual bismuth in warm nitric acid. The authors also noted that these crystals could not be prepared by the vapor transport technique and using melts based on Cu, Sn, In, S, and Te. Crystals of RuS2 (analogue of laurite), RuSe2 and RuTe2 in sizes up to 4 mm were grown in bismuth, and tellurium, respectively, using evacuated silica-glass tubes, cooled from 1000 C at a rate of 2 C per hour (Foise et al., 1985). Due to density differences, crystals of Ru chalcogenides grew above the melt. However, crystals grown in bismuth melts may contain some admixture of Bi, up to 3%. The same approach was also applied by Ezzaouia et al. (1985) to grow crystals of RuS2 in a tellurium flux by cooling from 1000 C to 850
700 C at rates of 0.7 or 1.4 C per hour. Iridium-rich crystals of RuS2 (Colell et al., 1994) were prepared from an initial mixture of Ir0.667xRu1-xS2 with bismuth, in a ratio 1:40, in an evacuated silica-glass tube, heated at 1100 C for a day. Afterwards the experiment was cooled to room temperature at a rate of 2 C per hour, and the crystals were washed in HNO3. It should be noted that often solid solutions of Ir-bearing crystals grown by cooling are zoned. Iron-doped RuS2 crystals (sizes up to 3 mm) were prepared by Tsay et al. (1994) using a tellurium flux (100 g of Te to 5 g of charge) cooling from 1000 C to room temperature at a rate of 1
0.7 C per hour. In order to obtain larger crystals, already-presynthetized crystals can be used as seed material. This approach was used by, e.g., Tsay et al. (1995), following Tsay et al. (1994), to grow crystals of RuS2, RuSe2, and RuTe2 reaching sizes of 15 3 10 3 10 mm. Os chalcogenides can be prepared using methods similar to the one used for Ru chalcogenides (Ezzaouia et al., 1984). Crystals of OsS2 were grown in sulfur and tellurium and OsSe2 in tellurium, with ratios of charge to solvent from 1:8 to 1:4 and 1:32 to 1:12, when using tellurium. The silica-glass tube with the charge was heated, in the case of tellurium, at 885 C for 12 hours and cooled to 600 C at a rate of 1 C per hour. For sulfur, the experiment was heated at 650 C and cooled to 300 C at the same rate. The resulting crystals, up to one mm in size, were washed from the tellurium in aqua regia and the sulfur was removed by evaporation (Ezzaouia et al., 1984). The growth of RuS2 and OsS2 crystals using the sulfur flux or RuTe2 and OsTe2 using tellurium flux can be considered as a self-flux technique. Applying a similar approach, crystals of Ir3Te8 were grown by cooling tellurium flux from 1000 C to 700 C (Liao et al., 1997) and platinumdoped IrTe2 crystals by cooling from 1160 C to 900 C (Pyon et al., 2013). The chalcogen flux can be applied to crystal growth of those chalcogenides that are in equilibrium with the respective chalcogen. The possibility of preparing only chalcogen-rich substances limits the self-flux technique. In cases where the solvent has a sufficient partial vapor pressure, then the crystals can be grown by evaporation resulting in crystals of monolayers growing at a constant temperature unlike what occurs during cooling. Zoned crystals are not formed. The application of evaporation can be nicely demonstrated by the crystal growth of RuS2, as documented by Fiechter and Ku¨hne (1987), and earlier by Ezzaouia et al. (1983, 1985). A boomerang-shaped silica-glass tube (by oxygen torch) was used as a reaction vessel (Fig. 10.2A). A tellurium or selenium melt containing RuS2 was placed in the left end of the vessel (growth

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FIGURE 10.2 Reaction vessels showing the growth of RuS2 crystals: (A) in selenium or tellurium flux by solvent evaporation. The solvent evaporates from the solution in the left part and condensates in the right part; (B) in bismuth flux under gradient conditions, with separated growth and dissolving zones; (C) in the traveling-solvent technique. Adapted from Fiechter, S., Ku¨hne, H.M., 1987. Crystal Growth of RuX2 (X 5 S, Se, Te) by chemical vapour transport and high temperature solution growth. J. Crystal Growth 83(4), 517
522.

zone) at 920 C; the solvent gradually evaporates and condenses at the right end of the ampoule at 900 C. Crystals of RuS2 grew up to 3 mm in size in 5 days and small crystals of RuTe2 (or RuSe2) were found in the melt. The authors also noted that bismuth is not suitable for this technique due to its low partial vapor pressure. However, they used a bismuth flux under gradient conditions. A sketch of the reaction vessel is shown in Fig. 10.2B. A silica-glass vessel about 14 cm long consists of two parts with a neck located approximately in the middle of the vessel. The neck enables RuS2 powder to float on the melt in the left part of the vessel and does not get into the right part (the crystallization zone). At the beginning of the experiment the entire vessel was held for a day at 1000 C, then the right part was cooled at a rate 2 C per hour to 500 C. As a result, crystals of RuS2 were grown with a surface area of up to 15 mm2. According to Fiechter and Ku¨hne (1987)

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FIGURE 10.3 A reaction vessel for salt-flux synthesis under temperature-gradient conditions for: (A) crystal growth of metals and alloys; (B) crystal growth of Ag-Pd chalcogenides.

this method is the most preferable for Ru chalcogenides. A traveling-solvent technique (Hurle et al., 1967) was applied by Fiechter and Ku¨hne (1987) for RuS2 crystal growth; a basic outline is shown in Fig. 10.2C. A silica vessel with a conical base (similar to the Bridgeman technique) and a conical tip with a neck on the other end is placed vertically. A hole is made in order that only a single nucleus is formed. In the beginning of the experiment the ampoule contains bismuth melt with RuS2 powder floating on it. The ampoule is slowly moved down at 0.01 mm/hour into a temperature gradient whereby crystals grow from the base fed by the charge that floats on the bismuth melt. Gradient conditions can be also applied to obtain some PGE intermetallic phases. For example, crystals (up to 1 mm) of platinum, palladium, and AuPd4 phase were grown in chlorides of alkali metals (Chareev, 2015). A schematic sketch of the synthesis is shown in Fig. 10.3A. The crystal growth was performed in a salt mixture of CsCl/KCl/NaCl, of eutectic composition in silica-glass tubes. A wire made of a noble metal, located along the length of the tube, serves as a source of that metal. The temperature at one end of the tube was about 600 C and in the other end about 50
100 C lower. The wire gradually dissolved at the hot end and formed metal crystals on the wire in the cold part of the tube. The metal ions migrate to the place of crystallization via the salt flux and electrons migrate along a wire. Likewise, using an electrically conducting wire it is possible to grow crystals of Ag-Pd chalcogenides (Chareev et al., 2016). The general scheme of the reaction vessel is shown in Fig. 10.3B. The silica-glass tubes were located in a temperature gradient; the hot end was at 450 C, and the cold end about 50  C lower. Material transport occurred in a LiCl-RbCl melt of eutectic composition. A charge of approximate (Ag,Pd)4X (where X was S or Se) composition, was placed at the hot end. A wire or a plate of palladium or silver-palladium alloy was touching the charge. After several weeks, small crystals of AgPd3Se (Fig. 10.4A), in an equilibrium association with Pd3Ag2S (coldwellite) and Pd4S (Fig. 10.4B) were obtained on the wire close to the charge. This technique can be confidently used to grow crystals only of those substances which are in equilibrium with silver-palladium alloy. This ongoing research, focused on

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FIGURE 10.4 Back-scattered electron images showing: (A) AgPd3Se crystals with a recrystallized Pd0.6Ag0.4 plate in the background; (B) equilibrium association of Pd3Ag2S (coldwellite) and Pd4S crystals.

transport of material under gradient conditions, has shown the possibility to grow PtS2 from FeS2 1 Pt charge in the (850-780 C) profile in eutectic NaCl/KCl.

10.5 PLATINUM-GROUP MINERALS AND SYNTHETIC ANALOGUES PGM recognized by the Commission on New Minerals, Nomenclature, and Classification (CNMNC) of the International Mineralogical Association (IMA) up to 2002 were summarized and thoroughly evaluated by Cabri (2002). All the pertinent information on the 109 PGM known at that time can be found in this review. An earlier summary of PGM was given by Cabri (1981a). Since 2002 an additional 27 new PGM have been described after approved by CNMNC IMA; in total there are 136 known PGM in 2016. In this chapter, we provide a brief summary of PGM described since Cabri’s overview. All 136 PGM known in 2016 are listed in Table 10.1. The ideal formulae are given as accepted by Cabri (2002); newly described PGM are marked with an a. Formulae for atheneite and mertierite II, based on new studies on the crystal structure and formulaes of telagpalite and keithconnite, are shown based on the study of the Ag-Pd-Te system by Vymazalov´a et al. (2015). A summary of PGM data with revised or newly determined crystal structures are presented in Table 10.2. The crystal structures of atheneite, chrisstanleyite, mertierite II, and sopcheite were newly determined, and using synthetic analogues for temagamite and tischendorfite. The crystal structure of atheneite was solved from data collected from a crystal from Itabira, Minais Gerais, Brazil; based on these results (Table 10.2), the formula was revised to be Pd2[As0.75Hg0.25] (Z 5 3) (Bindi, 2010), instead

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of the previously reported (Pd,Hg)3As (Z 5 2) (Clark et al., 1974). The crystal structure of mertierite II was reinvestigated on crystals from the Kaarrojja river, Inari commune, Polar Finland by Karimova et al. (in press), and yielded a formula of that is in agreement with the suggestion of Cabri (2002), proposing the 5:1 ratio for Sb:As. The crystal structure of sopcheite was solved using single-crystal data from the Lukkulaisvaara intrusion, northern Russian Karelia (Table 10.2; Laufek et al.,in press). Cooperite (PtS), some of whose phase relations were studied by Cabri et al. (1978), was reinvestigated in terms of crystal structure by Rozhdestvina et al. (2016). They found that in addition to the main reflections (corresponding to the known tetragonal cell, P42/mmc) there are many weak reflections which fit the tetragonal cell (I4/mmm) with double parameters. The crystal structures of isomertieite and to¨rnroosite were refined (Karimova et al., 2016). Table 10.3 summarizes new PGM described after 2002. As pointed out by Cabri (2002) there is still a significant number of PGM that require re-examination, re-definition or additional data for better characterization, particularly in terms of ideal formula and crystal structure. The main reason for the lack of insufficient identification of PGM is their mode of occurrence (as minute inclusions), intergrowths with other PGM, often embedded in base-metal sulfides and in most cases of very rare occurrence. These peculiarities often prevent XRD-based structural study. Therefore, in some cases further studies of synthetic analogues including crystal structure determination of PGM are desirable, ideally with natural minerals being investigated at the same time. Among newly described PGM (Table 10.3) the synthetic analogues were used in the description of the following mineral species: jacutingaite, milotaite, paˇsavaite, zaccariniite, lukkulaisvaaraite, kojonenite, palladosilicide, and norilskite. The XRD data were collected and crystal-structure studies were performed on their synthetic analogues, using either single crystals or powder samples. Consequently, the identity of a natural phase can be verified by a synthetic sample. The optical properties, physical properties, and chemical composition must be in agreement. In order to prove the structural identity, various methods can be used. The best way is to compare the X-ray diffraction data of a natural sample with its synthetic analogue (e.g., kitagohaite, sudburyite) but the extraction of a suitable grain of the natural sample is not always possible. Therefore, in order to prove the structural identity of natural and synthetic sample Electron Backscatter Diffraction or Raman spectroscopy (e.g., zaccariniite) can be applied. However, Raman spectroscopy has limited success, particularly among PGE alloy phases. Electron Backscatter Diffraction (EBSD), a technique based on the scanning electron microscope, enables sample microstructure to be analyzed, visualized, and quantified; it is a non-destructive method for the study of tiny grains, in situ (in polished sections). The diffraction pattern is characteristic of the crystal structure and orientation in the spot where it was generated. Hence the diffraction pattern can be used to determine the crystal orientation, discriminate between crystallographically different phases, characterize grain boundaries, and provide information about the local crystalline perfection. EBSD was used for the description of jacutingaite, paˇsavaite, lukkulaisvaaraite, kojonenite, palladosilicide, and norilskite. The EBSD technique can be applied as a supporting tool in order to distinguish various PGM minerals with defined crystal structures, but does not work in every case, depending on the polished characteristics of different minerals. We tabulate all known PGM in 2016 (Table 10.1) and provide a brief overview on new PGM described from 2002 to 2016, as summarized in Table 10.3. Minerals are listed in alphabetical order; the data were collected from the original sources. All listed minerals were approved by the CNMNC of IMA and resulted in a publication except for ferhodsite (IMA No

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2009-056, Begizov). The mineral was accepted by the Commission in 2009 but the description has not yet been published so that insufficient information about the mineral composition and other properties is known. Reflectance data for all listed minerals were measured in the range of λ from 400 to 700 nm (in case of paˇsavaite and jacutingaite from λ 420 to 700 nm). Herein we present only four wavelengths recommended by COM. The strongest lines from the XRD patterns are given, with a reference to the PDF or ICSD databases, if known. An average of electron-microprobe analyses (EMPA) is given for chemical composition. The experimental aspects for the corresponding compound are discussed for each mineral/synthetic analogue. Minerals marathonite Pd25Ge9 (IMA No 2016-080), palladogermanide Pd2Ge (IMA No 2016086), kravtsovite PdAg2S (IMA No 2016-092) and vymazalov´aite Pd3Bi2S2 (IMA No 2016-105) were accepted when this Chapter was completed therefore a detailed description of these four minerals is not provided.

10.5.1 BORTNIKOVITE PD4CU3ZN Crystallography: tetragonal, P4/mmm ? ˚ , V 306.0 A ˚ 3, Z 53 Unit cell: a 6.00, c 8.50 A ˚ (I)(hkl)]: 3.00(1)(200,112), 2.64(1) X-ray powder diffraction pattern, strongest lines [d in A (120), 2.36(0.5)(113), 2.13(10)(004, 220), 1.737(1)(132), 1.501(3)(400,224), 1.346(2)(240,332), 1.224(8)(404), 1.161(1)(151), 1.059(4)(440), ICDD PDF2 card 00-060-0492 Structure: not defined Appearance: Forms rims (50
60 μm thick and 50
150 μm long) on isoferroplatinum, intergrowing with titanite and chlorite. Found in a heavy concentrate sample from sediments of the Konder valley. Optical properties: White with a slight greyish tint in reflected light; bireflectance, anisotropy, and internal reflections not observed. Reflectance, [λnm, R %]

470 546 589 650

56.9 61.7 63.4 65.4

Physical Properties: Opaque, metallic luster, steel-white with slight cream tint, poorly malleable Hardness: VHN25 367.9 (354
382) kg/mm2 Mohs Cleavage: not observed Density: 11.16 g/cm3 (calc.) Chemical Composition (EMPA data, wt.%): P Pd 58.19, Pt 4.06, Fe 1.41, Cu 27.26, Zn 8.02 98.94(Pd3.82Pt0.14)P3.96Cu3.00(Zn0.86 P Fe0.18) 1.04 (n 510) P Pd 62.44, Cu 27.97, Zn 9.59 100.00 Pd4Cu3Zn—ideal Type locality and occurrence: The Konder placer deposit, Ayan-Maya district, Khabarovsky krai, Russia.

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327

Name: For Nikolai S. Bortnikov of the Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry RAS, in recognition of his contributions to mineralogy and mineral deposits. Reference: Mochalov et al. (2007), IMA No 2006-027 Note: Further investigations on XRD data and crystal structure is desirable. Experimental: The phase diagram of the Pd-Cu-Zn system at 400 C and 800 C was assessed tentatively by Lebrun et al. (2007), based on data of Dobersek and Kosovinc (1989). The corresponding synthetic phase is not known. A further, more detailed experimental study is needed.

10.5.2 COLDWELLITE PD3AG2S Crystallography: Cubic, P4332 ˚ , V 380.61 A ˚ 3, Z 5 4 Unit cell: a 7.2470 A ˚ (I)(hkl)]: 2.427(100)(221), 2.302(38) X-ray powder diffraction pattern, strongest lines [d in A (310), 2.195(38)(311), 1.4280(44)(510,431), 0.9294(24)(650,643), 0.9208(20)(732,651) Structure: isostructural with β-Mn Appearance: Discovered in a high-grade heavy-mineral concentrate from the Marathon deposit. Coldwellite (in size 150 3 80 μm), is anhedral, slightly angular with scalloped grain edges with overgrowth of vysotskite (PdS); most coldwellite occur in small grains, sizes 0.5
11 μm. Optical properties: In reflected light white with a light pinkish brown tint, isotropic. Reflectance [λnm, R%]

470 546 589 650

41.9 44.9 44.0 45.0

Physical Properties: Opaque, with a metallic luster Hardness: not measured Cleavage: not observed Density: 9.90 g/cm3 (calc.) Chemical Composition (EMPA data, P wt.%): Pd 56.10 Fe 0.16 Ag 38.20P S 5.63 100.09, (Pd2.99Fe0.02)P3.01Ag2.00S0.99 (n 5 23) Pd 56.30 Ag 38.05 S 5.65 100.00, Pd3Ag2S—ideal Type locality and occurrence: The Marathon Cu-PGE-Au deposit, Coldwell Complex, Ontario, Canada (48 480 7v N, 86 180 55v W). It was also reported from the PGE-Cr zone of the Birch Lake Deposit, Duluth Complex, Canada (Severson and Hauck, 2003) and in PGE mineralization of the Fedorova-Pana ore node (Subbotin et al., 2012). Name: After the locality at the Coldwell Complex, Ontario, Canada. Reference: McDonald et al. (2015), IMA No 2014-045 Experimental: The synthetic analogue occurs as a distinct phase in the ternary system Pd-Ag-S at 400 C and 550 C (Vymazalov´a et al., in prep). Based on the experimental study (Ag2S-Pd) of Raub (1954) the phase Pd3Ag2S is stable up to 940 C.

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10.5.3 FERHODSITE (FE,RH,NI,IR,CU,PT)9S8 Crystallography: Tetragonal ˚ , V 985.77 A ˚3 Unit cell: a 10.009, c 9.840 A ˚ (I)(hkl)]: 5.72(50), 3.01(70), 2.81(30), X-ray powder diffraction pattern, strongest lines [d in A 2.23(100), 1.933(60), 1.772(40), 1.367(3), 1.167(4) Type locality and occurrence: Nizhny Tagil ultramafic complex, Solovyeva Gora, Alexandrov Log (57 400 N, 59 390 W) and the Konder placer, Konder alkaline-ultrabasic massif, Maya river basin, South Yakutia, Russia (57 360 N, 134 370 W). Name: For the main chemical components (Fe, Rh, S). Reference: Begizov V.D., IMA No 2009-056 Note: Approved by IMA in 2009 but no other data on the mineral have been published to date.

10.5.4 JACUTINGAITE PT2HGSE3 Crystallography: trigonal, P3m1 ˚ , V 247.59 A ˚ 3, Z 5 2 Unit cell: a 7.3477, c 5.2955 A ˚ (I)(hkl)]: 5.2917(100)(001), 2.7273(16) X-ray powder diffraction pattern, strongest lines [d in A (201), 2.4443(10)(012), 2.0349(18)(022), 1.7653(37)(003), 1.3240(11)(004) 1.0449(11)(025) Structure: The crystal structure was solved and refined from the powder X-ray-diffraction data on synthetic Pt2HgSe3. Isostructural with Pt4Tl2X6 (X 5 S, Se, or Te); no structural analogue is known as a mineral. Appearance: Occurs as a single grain (about 50 μm across) in an aggregate (2 mm across) of atheneite, potarite, and hematite, obtained from a heavy-mineral concentrate. Optical properties: Light gray in reflected light, bireflectance moderate to distinct, a bluish gray to rusty brown pleochroism; anisotropy weak to distinct. Reflectance [λnm, R1, R2 %]

470 546 589 650

47.4 48.2 48.0 47.1

51.1 50.5 49.6 47.8

Physical Properties: Opaque, gray with a metallic luster and gray streak, brittle. Hardness: VHN10 169 (119
245) g/mm2, Mohs 31/2 Cleavage: {001} very good Density: 10.35 g/cm3 (calc.), 10.9 (meas. on synth.) Chemical Composition (EMPA data, wt.%): P Pt 37.30, Pd 5.91, Hg 25.72, Ag 0.16, Cu 0.82 Se 31.48 101.39 (Pt1.46Pd0.42Cu0.10 Ag0.01)P1.99Hg0.98Se3.04 (n 53) P Pt 46.73, Hg 24.06, Se 28.33 P99.12 Pt1.97Hg1.04Se2.99 (synth., n 57) Pt 47.14, Hg 24.24, Se 28.62 100.00 Pt2HgSe3—ideal Type locality and occurrence: The Caueˆ iron-ore deposit, Itabira district, Minas Gerais, Brazil Name: After the specular hematite-rich vein-type gold mineralization, locally known as “jacutinga,” in which the mineral occurs.

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329

Reference: Vymazalov´a et al. (2012a), IMA No 2100-078 Note: The structural identity of natural and synthetic Pt2HgSe3 was confirmed by electron backscattering diffraction (EBSD). Experimental: Phase relations in the system Pd-Hg-Se were studied at 400 C (Dr´abek et al., 2012). Only one ternary phase (jacutingaite) is known in the ternary system. Jacutingaite forms stable assemblages with tiemannite (HgSe) and sudovikovite (PtSe2), sudovikovite and luberoite (Pt5Se4), luberoite and platinum, and coexists with PtHg, PtHg2, PtHg4 phases. Below 250 C, the phase HgPt is no longer stable and the assemblage Pt2HgSe3 1 PtHg2 1 (PtHg)ss appears in the system.

10.5.5 JAGUE´ITE CU2PD3SE4 Crystallography: monoclinic, P21/c ˚ , β 115.403 , V 318.0 A ˚ 3, Z 5 2 Unit cell: a 5.6719, b 9.9095, c 6.2636 A ˚ (I)(hkl)]: 2.759(23),2.676(100)(121), X-ray powder diffraction pattern, strongest lines [d in A 2.630(64)(122), 2.508(31)(202), 2.269(27)(041), 1.950(27)(122), 1.920(36)(123), 1.866(24)(241), ICDD PDF2 card -00-057-0615 Structure: Structure solved from a single crystal by Topa et al. (2006), isostructural with chrisstanlyeite. Appearance: Occurs in lobate aggregates with chrisstanleyite (up to 500 μm in across) embedded in calcite or as inclusions of anhedral grains (up to 50 μm across) in tiemannite and naumannite with common twinning. Optical properties: Light creamy-yellowish in reflected light, bireflectance weak to moderate, pleochroic from a light buff to a creamy buff, strong anisotropy (rotation tints from brownish to bluish, greenish). Reflectance, [λnm, R1, R2 %]

470 546 589 650

air 41.0 50.1 44.1 51.8 44.6 51.7 45.1 52.0

im 27.0 29.2 29.4 30.2

31.9 33.8 33.7 34.1

Physical Properties: Opaque with a metallic luster and black streak, brittle, uneven fracture. Hardness: VHN25 612 (464
772) g/mm2, Mohs 5 Cleavage: not observed Density: 8.02 g/cm3 (calc.) Chemical Composition (EMPA data,P wt.%): Cu 15.7, Ag 1.59 Pd 42.04, SeP 40.15 99.48 (Cu1.91Ag0.11)P2.02Pd3.05Se3.93 (n 5 8) Cu 16.68, Pd 41.88, Se 41.44 100.00 Cu2Pd3Se4—ideal Type locality and occurrence: Selenide mineralization at El Chire, the depression of Jagu´e La Rioja province, Argentina (28 38.30 S, 68 44.30 W). Observed, as an unnamed phase, from the Copper Hills occurrence, East Pilbara region, Western Australia (Nickel, 2002). Name: After the village of Jagu´e, the closest settlement to the El Chire mine, La Rioja, Argentina. Reference: Paar et al. (2004), Topa et al. (2006), IMA No 2002-60

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Experimental: The synthetic analogue occurs as a distinct phase in the ternary system Pd-CuSe at 300 and 400  C (Makovicky and Karup-Møller, in press).

10.5.6 KALUNGAITE PDASSE Crystallography: Cubic, Pa3 ˚ , V 225.78 A ˚ 3, Z 5 4 Unit cell: a 6.089 A ˚ (I)(hkl)]: 3.027(75)(002), 1.838(100) X-ray powder diffraction pattern, strongest lines [d in A (113), 1.172(95)(115,333), 1.077(80)(044,144,334), 0.988(70)(116,235,253), 0.929(90)(335), 0.918 (70)(226), ICDD PDF2 card 00-058-0509 Structure: not defined Appearance: Occurs as 0.1
0.5 mm platy anhedral aggregates, in association with gold, chalcopyrite, bohdanowiczite, clausthalite, guanajuatite, Pb-Bi-Se-S phase, padmaite, sperrylite, stilbiopalladinite. Optical properties: In reflected light cream, creamy gray against gold, isotropic, no internal reflections. Reflectance, [λnm, R %]

470 546 589 650

air 47.5 46.9 46.8 48.0

im 33.3 32.6 32.6 34.0

Physical Properties: Lead gray with metallic luster, black streak, brittle with an uneven fracture Hardness: VHN25 438 (429-455) g/mm2, Mohs Cleavage: not observed Density: 7.59 g/cm3 (calc.) Chemical Composition (EMPA data, wt.%): P Pd 41.32, As 27.49, Bi 0.35, Sb 1.59, Se 27.67, S 1.22 99.64 Pd1.01(As0.95Sb0.03Bi0.004) P P 0.98(Se0.91S0.10) 1.01 (n58) P Pd 40.88, As 28.78, Se 30.34 100.0 PdAsSe—ideal Type locality and occurrence: The Buraco do Ouro gold mine, Cavalcante town, Goi´as State, Brazil (13 470 45v S, 47 270 35v W). Name: For the Kalunga people, a community of descendants of African slaves living in the surroundings of the mine, Goi´as State, Brazil. Reference: Botelho et al. (2006), IMA No 2004-047 Note: The XRD data of natural sample are in an agreement with the data of the synthetic phase (ICDD PDF2—01-070-8016 card) and would be worth reinvestigation in terms of refinement based on the structural model proposed by Foecker and Jeitschko (2001). Experimental: The ternary system Pd-As-Se has not been investigated. Nevertheless, the synthetic analogue was studied by Foecker and Jeitschko (2001). They refined the crystal structure of the synthetic PdAsSe from the single crystal XRD data. The phase is cubic, space group P213, a ˚ , V 226.40 A ˚ 3, Z 4, and belongs to the ullmannite (NiSbS) type structure. 6.095 A

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331

10.5.7 KINGSTONITE RH3S4 Crystallography: monoclinic, C2/m ˚ , β 109.000 , V 666.34 A ˚ 3, Z 56 Unit cell: a 10.4616, b 10.7527, c 6.2648 A ˚ (I)(hkl)]: 3.156(100)(310), 3.081(100)(131), 2.957(90) X-ray powder diffraction pattern, [d in A (002), 2.234(60)(202), 1.941(50)(223), 1.871(80)(441), 1.791(90)(060,133) Structure: Structure solved and refined from single crystal. A new structure type. Appearance: Occurs as subhedral (tabular, elongate) to anhedral inclusions (10
40 μm) in PtFe alloy with isoferroplatinum, tetraferroplatinum, Cu-bearing Pt-Fe alloy, osmium, enriched oxide remnants of osmium, laurite, bowieite, ferrorhodsite, cuprorhodsite. Optical properties: In reflected light pale slightly brownish gray, weakly pleochroic, weak bireflectance, weak to moderate anisotropy (rotation tints in dull grays and browns). Reflectance, [λnm, R1, R2 %]: 470 air 47.2 48.9 im 33.2 34.7, 546 48.4 50.3 34.3 36.1 589 49.1 50.7 35.0 36.5 650 49.8 51.0 35.6 36.7 Physical Properties: Opaque with a metallic luster and black streak, brittle. Hardness: VHN25 895 (871
920) g/mm2, Mohs 6 Cleavage: good, parallel to [001] Density: 7.52 g/cm3 (calc.) Chemical Composition (EMPA P data, wt.%): Rh 46.5, Ir 16.4, Pt P 11.2, S 25.6 99.7 (Rh2.27Ir0.43Pt0.29)P2.99S4.01 (n 520) Rh 70.65, S 29.35, 100.00 Rh3S4—ideal Type locality and occurrence: The Bir Bir river, Wallaga province, Yubdo district, Ethiopia. Also observed as inclusions in heavy-concentrate platinum from diamond placers of the MayatVodorazdel’nyi site in the Anabar river basin, Russia (Airiyants et al., 2014). Name: For Gordon A. Kingston (b. 1939), in recognition of his contributions to PGE mineralogy and geology of related deposits. Reference: Stanley et al. (2005), IMA No 1993-46 Experimental: The mineral has a synthetic analogue Rh3S4 (Beck and Hilbert, 2000; ICSD No 410813, ICDD PDF2 01-070-5129), stable up to 1130 C. The binary system Rh-S comprises another three binary phases Rh17S15, Rh2S3 and RhSB3 (Predel, 1998). Based on the study of the ternary system Cu-Rh-S by Karup-Møller and Makovicky (2007), the phase Rh3S4 dissolves up to 0.6 Cu and 2.8 at.% Cu at 900 C and 700 C, respectively and is not stable at 540 C. The natural mineral may be stabilized by the content of Pt or Ir at lower temperature.

10.5.8 KITAGOHAITE PT7CU Crystallography: Cubic, Fm3m ˚ , V 472.57 A ˚ 3, Z 5 4. Unit cell: a 7.7891 A ˚ (I)(hkl)]: 2.246(100)(222), 1.948(8) X-ray powder diffraction pattern, strongest lines [d in A (004), 1.377(77)(044), 1.174(27)(622), 1.123(31)(444), 0.893(13)(662)

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Structure: Ca7Ge type. The XRD data of kitagohaite were refined by the Rietveld method based on the structural model of a synthetic analogue (Schneider and Esch, 1944; Sluiter et al., 2006) (ICSD No 108775, ICDD PDF2 01-074-6150 card). Appearance: The mineral comes from a heavy-mineral concentrate. It occurs in grains (around 0.5 mm in size), rimmed by hongshiite (PtCu). Optical properties: In reflected light, white, isotropic. Reflectance [λnm, R%]

470 546 589 650

63.2 66.6 68.2 70.1

Physical Properties: Opaque, greyish white, with a metallic luster and gray streak, malleable. Hardness: VHN100 217 (206-237) g/mm2, Mohs 31/2 Cleavage: not observed Density: 19.958 g/cm3 (calc.) Chemical Composition (EMPA data, wt.%): P Pt 95.49, Cu 4.78 P100.26 Pt6.93Cu1.07 (n 513) Pt 95.55, Cu 4.45 100.00 Pt7Cu—ideal Type locality and occurrence: The Lubero region of North Kivu, Democratic Republic of the Congo. Name: For the Kitagoha river, the platiniferous river in the Lubero region, Congo. Reference: Cabral et al. (2014), IMA No 2013-114 Experimental: It has a synthetic analogue CuPt7 (Schneider and Esch, 1944), with an ordered structure whereas above 500 C it becomes disordered, lacking superlattice reflections.

10.5.9 KOJONENITE PD7-XSNTE2 (0.3 # X # 0.8) Crystallography: tetragonal, I4/mmm ˚ , V 335.0 A ˚ 3, Z 5 2 Unit cell: a 4.001, c 20.929 A ˚ (I)(hkl)]: 10.465(29)(002), 2.496(52) X-ray powder diffraction pattern, strongest lines [d in A (114), 2.1986(100)(116), 2.0930(18)(0010) 2.0025(48)(200), synth. (ICSD PDF2 cards 01-073-5652 and PDF 01-073-9276) Structure: Structure solved on a synthetic single crystal by Savilov et al. (2005), and confirmed by x-ray powder diffraction data on experimental products (Vymazalov´a and Dr´abek, 2010). Isotypic to nickel analogues of Ni7-xSnQ2 (Q 5 S, Se, Te) (Baranov et al., 2003, 2004), consists of Cu3Au-like Sn/Pd blocks and NaCl-like Pd/Te slabs. Appearance: It forms anhedral grains (, 40 μm) in aggregates (up to 100 μm) with kotulskite as inclusions in chalcopyrite and cubanite. Optical properties: In reflected light slightly pinkish off-white against (kotulskite bright cream), weak bireflectance (visible only on differently oriented adjacent grains), no pleochroism, anisotropy distinct (with rotation tints in shades of dark greenish-brown).

10.5 PLATINUM-GROUP MINERALS AND SYNTHETIC ANALOGUES

Reflectance, [λnm, Ro, Re0 %]

470 546 589 650

nat. 55.0 52.7 58.5 56.5 61.0 58.3 63.9 60.1

333

synth. 54.8 53.4 58.6 56.9 61.2 59.4 63.8 61.4

Physical Properties: Opaque, metallic luster, brittle, black streak (synth.). Hardness: not measured Cleavage: not observed Density: 10.07 g/cm3 (calc.) Chemical Composition (EMPA Pdata, wt.%): Pd 62.48, Sn 11.74, Te 25.63 99.85 Pd5.96Sn1.00Te2.04 (n 5 20), Pd 63.1, Sn 11.7, Te 25.2— simplified formula for naturalPsample Pd6SnTe2. P Pd 63.8 Sn 11.5 Te 24.7 100.0 for x5 0.8; Pd 65.6 Sn 10.9 Te 23.5 100.0 for x 50.3 Pd7-xSnTe2—ideal based on crystal structure of synthetic material. Type locality and occurrence: the Stillwater Layered Igneous Intrusion, Stillwater Valley, Montana, USA (45 230 11v N, 109 530 03v W). The mineral is known also to occur in Noril’sk ores (Sluzhenikin et al., pers. comm.). Name: For Kari K. Kojonen (b. 1949) of the Geological Survey of Finland, for his contributions to ore mineralogy. Reference: Stanley and Vymazalov´a (2015), IMA No 2013-132 Note: The structural identity between natural and synthetic kojonenite was confirmed by electron backscatter diffraction (EBSD). Experimental: Phase relations in the system Pd-Sn-Te were determined at 400 C (Vymazalov´a and Dr´abek, 2010). At 400 C the system contains three ternary compounds: kojonenite, and phase Pd72Sn16Te12 and PdSnTe, not known to occur in nature. Kojonenite forms a stable assemblage with paolovite (Pd2Sn, dissolving up to 4 at.% Te) and the ternary phase Pd72Sn16Te12. It also coexists with palladium tellurides kotulskite (PdTe), phase Pd3Te2, telluropalladinite (Pd9Te4), and keithconnite (dissolving up to 4 at.% Sn). The upper stability of kojonenite is 596 C where it melts incongruently.

10.5.10 LISIGUANGITE CUPTBIS3 Crystallography: Orthorhombic, P212121 ˚ , V 487.80 A ˚ 3, Z 54 Unit cell: a 7.7152, b 12.838, c 4.9248 A ˚ (I)(hkl)]: 6.40(30)(020), 3.24(80)(031), X-ray powder diffraction pattern, strongest lines [d in A 3.03(100)(201), 2.27(40)(051), 2.14(50)(250), 1.865(60)(232) Structure: The crystal structure was solved from a single crystal fragment. Belongs to the lapieite group, Pt-analogue of mu¨ckeite (CuNiBiS3) and malyshevite (PdCuBiS3). Appearance: Occurs as idiomorphic crystals, generally tabular or lamellae {010}, elongated along [100], up to 2 mm long and 0.5 mm wide. Sampled from a heavy mineral concentrate. Optical properties: In reflected light, bright white with a yellowish tint, anisotropy weak to moderate (blue-greenish to brownish colors and parallel-axial extinction), no internal reflection, parallel extinction.

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Reflectance, [λnm, R1 R2 %]

470 546 589 650

air 39.2 36.7 40.3 37.3 40.7 37.9 40.8 37.9

im 23.4 22.3 23.6 22.6 23.6 22.7 23.7 22.9

Physical Properties: Opaque, lead-gray with black streak and metallic luster, brittle Hardness: VHN25 48.3 (46.7
49.8) g/mm2, Mohs 21/2 Cleavage: {010} perfect, {001} distinct, {100} visible Density: 7.42 g/cm3 (calc.) Chemical Composition (EMPA data, wt.%): P Cu 12.98, Pt 30.04, Pd 2.69, Bi 37.65, S 17.55 100.91 Cu1.10(Pt0.83Pd0.14)P0.97Bi0.97S2.96 (n 5 8) P Cu 11.27, Pt 34.60, Bi 37.07, S 17.06 100.00 CuPtBiS3—ideal Type locality and occurrence: Mineral discovered in a PGE-bearing Co-Cu sulfide vein in garnet pyroxenite of the Yanshan Mountains, Chengde Prefecture, Hebei Province, China. The mineral also observed in Cu-Ni-PGE ores in the footwall of the Sudbury Igneous Complex, Canada (Pentek et al., 2013). Name: After Li Siguang on the 120th anniversary of his birth (1889
1971); prominent Chinese geologist, a founder of geomechanics, advocate of the theory of tectonic systems, one of the pioneers in oil exploration in China. Reference: Yu et al. (2009), IMA No 2007-003 Experimental: The quaternary system Cu-Pt-Bi-S has not been experimentally studied. The preliminary experimental results of ongoing research confirm the existence of a synthetic analogue stable at 400 C.

10.5.11 LUKKULAISVAARAITE PD14AG2TE9 Crystallography: tetragonal, I4/m ˚ , V 949.1 A ˚ 3, Z 5 2. Unit cell: a 8.9599, c 11.822 A ˚ (I)(hkl)]: 2.8323(58)(130,310), 2.8088(92) X-ray powder diffraction pattern, strongest lines [d in A (213), 2.5542(66)(312), 2.4312(41)(321,231), 2.1367(57)(411,141), 2.1015(52)(233,323), 2.0449(100) (314), 2.0031(63)(420,240), 1.9700(30)(006), 1.4049(30)(246,426), 1.3187(36)(543,453) (synth.). Structure: The crystal structure was solved and refined from the powder X-ray-diffraction data of synthetic Pd14Ag2Te9. Unique structure type; shows some similarities to that of sopcheite (Ag4Pd3Te4) and palladseite (Pd17Se15). Appearance: Occurs as anhedral grains (about 40 μm in diameter) rimmed by tulameenite and randomly accompanied by telargpalite and Bi-rich kotulskite, enclosed in chalcopyrite, in association with millerite, bornite and hematite. It also is observed as tiny grains (5
10 μm) in intergrowths with telargpalite and Bi-rich kotulskite in association with moncheite, tulameenite, hongshiite, and telluropalladinite. Optical properties: In reflected light, light gray with a brownish tinge, strong bireflectance, light brownish gray to greyish brown pleochroism, distinct to strong anisotropy; exhibits no internal reflections.

10.5 PLATINUM-GROUP MINERALS AND SYNTHETIC ANALOGUES

Reflectance, [λnm, R1 R2 %]

470 546 589 650

40.9 47.6 52.1 57.5

335

48.3 56.4 61.0 65.2

Physical Properties: Opaque, gray, with metallic luster, and gray streak, brittle. Hardness: VHN20 355 (339
371) kg/mm2, Mohs 4 Cleavage: not observed Density: 9.993 g/cm3 (calc.), 9.9 g/cm3 (meas. on synth.) Chemical Composition (EMPA P data, wt.%): Pd 52.17, Ag 7.03, Te 40.36 P99.56 Pd14.05Ag1.88Te9.06 (n 5 5) Pd 52.13, Ag 7.31, Te 40.58 P100.02 Pd13.99Ag1.93Te9.08 (synth. n 5 9) Pd 52.20, Ag 7.56, Te 40.24 100.00 Pd14Ag2Te9—ideal Type locality and occurrence: The Lukkulaisvaara intrusion, northern Russian Karelia, Russia. (66 190 20v N, 30 490 50v E). Also observed, as an unnamed phase, in the South Sopcha massif and from the Monchetundra deposit of the Monchegorsk Complex, Kola Peninsula, Russia (Grokhovskaya et al., 2003, 2009). Name: For the Lukkulaisvaara intrusion in Russian Karelia. Reference: Vymazalov´a et al. (2014a), IMA No 2013-115 Note: The structural identity between natural and synthetic Pd14Ag2Te9 was confirmed by electron backscatter diffraction (EBSD). Experimental: Phase relations in the system Pd-Ag-Te were determined at 350 C and 450 C (Vymazalov´a et al., 2015). At 350 C the system contains five ternary compounds: sopcheite (Pd3Ag4Te4), lukkulaisvaaraite (Pd14Ag2Te9), telargpalite (Pd22xAg11xTe 0.09 , x , 0.22), and phases Pd7.5-xAg0.51xTe3 (0.02 , x , 0.83) and Pd21xAg2-xTe (0.18 , x , 0.24). Lukkulaisvaaraite coexists with kotulskite and sopcheite, hessite and sopcheite, telargpalite and hessite; it forms stable associations with the phase Pd3Te2 and kotulskite, and with Pd3Te2 and telluropalladinite. It also coexists with a phase Pd7.5-xAg0.51xTe3 and telargpalite, with the phase Pd7.5-xAg0.51xTe3 and telluropalladinite. At 450 C, sopcheite is no longer stable and the assemblage lukkulaisvaaraite 1 kotulskite 1 hessite become stable.

10.5.12 MALYSHEVITE PDCUBIS3 Crystallography: Orthorhombic, Pnam ˚ , V 563.204 A ˚ 3, Z 5 4 Unit cell: a 7.541, b 6.4823, c 11.522 A ˚ (I)(hkl)]: 3.24(4)(020), 2.88(8)(004), X-ray powder diffraction pattern, strongest lines [d in A 2.52(6)(300), 1.900(10)(304), 1.715(2)(206), 1.672(2)(225), ICDD PDF2 card—00-060-0390. Structure: not determined, chemically Pd-analogue of lisiguangite Appearance: Malyshevite forms rims (1
20 μm) around clausthalite, replacing padmaite. Optical properties: In reflected light, white, bireflectance moderate, a bright yellow to pale yellow pleochroism; anisotropy weak to distinct (light yellow tints).

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Reflectance, [λnm, R1 R2 %]

470 546 589 650

34.1 36.3 37.0 37.4

28.7 33.0 34.4 34.6

Physical Properties: Bluish gray, with metallic luster and gray streak. Hardness: VHN not measured, Mohs 3 Cleavage: not observed Density: 6.025 g/cm3 (calc.) Chemical Composition (EMPA data, wt.%): P Pd 20.6, Pt 1.0, Pb 0.8, Bi 42.6, Cu 13.1, Se 2.2, S 19.0 99.3 (Pd0.94Pt0.02Pb0.02)P0.98Bi0.99 Cu1.00(S2.88Se0.14)P3.02 (n 5 7) P Pd 22.39, Cu 13.38, Bi 43.99, S 20.24 100.00 PdBiCuS3—ideal Type locality and occurrence: The Srednyaya Padma U-V deposit in Southern Karelia, Russia. The mineral also observed in Cu-Ni-PGE ores in the footwall of the Sudbury Igneous Complex, Canada (Pentek et al., 2013), and in Noril’sk ores (Spiridonov et al., 2015) and is found in intergrowths with its Pt-analogue lisinguaite from its type locality (Yu et al., 2009). Name: In honor of I.I.Malyshev (1904
1973) and V.I. Malyshev (1927
2002), father (who first discovered the Malyshevskoe—Samotkanskoe Ti deposit) and son, formerly of the All-Russian Scientific-Research Institute of Mineral Resources (VIMS). Reference: Chernikov et al. (2006), IMA No 2006-012 Note: Further investigations of the crystal structure are needed. Experimental: The quaternary system Cu-Pd-Bi-S has not been experimentally studied.

10.5.13 MIESSIITE PD11TE2SE2 Crystallography: cubic, Fd3m ˚ , V 1929.0 A ˚ 3, Z 5 8 Unit cell: a 12.448 A ˚ (I)(hkl)]: 2.395(80)(511,333), 2.197 X-ray powder diffraction pattern, strongest lines [d in A (100)(440), 1.875(25)(622), 1.555(25)(800), 1.305(25)(931), 1.271(30)(844), ICDD PDF2 card— 00-059-0323. Structure: Isostructural with isomertierite (Pd11As2Sb2) and to¨rnroosite (Pd11As2Te2). Appearance: Discovered with placer gold and PGM nuggets, as one grain (483 3 522 μm). Shows a subidiomorphic cubic morphology. Optical properties: In reflected light, light gray, isotropic. Reflectance, [λnm, R%]

470 546 589 650

48.88 51.63 53.91 56.82

Physical Properties: Opaque, black with a metallic luster, malleable. Hardness: VHN100 362 (348-370) g/mm2, Mohs 2
21/2

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337

Cleavage: not observed Density: 10.94 g/cm3 (calc.) Chemical Composition (EMPA P data, wt.%): Pd 75.17, Te 17.06, Se 9.61 P101.84 Pd11.02Te2.09Se1.90 (n 516) Pd 73.91, Te 16.12, Se 9.97 100.00 Pd11Te2Se2—ideal Type locality and occurrence: The Miessijoki River in the Lemmenjoki area, Inari commune, Finnish Lapland, Finland (25 210 N, 68 250 E). Name: For the Miessi river, Finnish Lapland (in the Saami language “Miessijohka,” where johka means river, and miessi a reindeer calf). Reference: Kojonen et al. (2007), IMA No 2006-013 Experimental: The synthetic analogue has not been studied; nor has the Pd-Te-Se system.

10.5.14 MILOTAITE PDSBSE Crystallography: cubic, P213 ˚ , V 252.20 A ˚ 3, Z 5 4 Unit cell: a 6.3181 A ˚ (I)(hkl)]: 2.825(100)(201), 1.905(98) X-ray powder diffraction pattern, strongest lines [d in A (311), 2.579(81)(211), 3.159(53)(200), 2.233(32)(220), 1.752(27)(320), 1.688(25)(312), 1.378(18) (412), ICDD PDF2 card—01-073-3935, synth. Structure: The crystal structure was determined on a single crystal of synthetic PdSbSe. The structure of PdSbSe is a homeotype of the structure of pyrite (FeS2) and an isotype of the cubic ordered structure of gersdorffite (NiAsS). Appearance: Occurs as subhedral grains (less than 25 μm in diameter), embedded in eucairite and tiemannite, randomly intergrown with a graphic intergrowth of bornite and selenian digenite. Optical properties: In reflected light, white, isotropic. Reflectance, [λnm, R%]

470 546 589 650

nat. 48.6 47.5 47.6 49.0

synth. 48.0 47.1 47.0 48.2

Physical Properties: Silvery gray, metallic luster, opaque, brittle, uneven fracture (synth.). Hardness: VHN100 465 (420
514) g/mm2 (synth.), Mohs 41/2 Cleavage: not observed Density: 8.09 g/cm3 (calc.), 7.98-8.23 g/cm3 (meas. on synth.) Chemical Composition (EMPA data, wt.%): P Pd 34.17, Cu 0.78, Ag 0.35, Sb 38.03, Se 26.38 99.71 (Pd0.98Cu0.04)P1.02(Ag0.01Sb0.95)P0.96 Se1.02 (n 5 5) P Pd 34.46, Sb 38.86, Se 26.60 P99.91 Pd0.99Sb0.97Se1.04 (synth., n 5 17) Pd 34.65, Sb 39.64, Se 25.71 100.00 Pd1Sb1Se1—ideal Type locality and occurrence: Pˇredboˇrice, a low-temperature selenide-bearing uranium mineralization in the Czech Republic. Name: For Milota Makovicky (b. 1941), University of Copenhagen, in recognition of her investigations of sulfide and sulfoarsenide systems with PGE.

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Reference: Paar et al. (2005), IMA No 2003-056 Note: X-ray powder-diffraction pattern derived from the crystal structure refinement. Identity between natural and synthetic PdSbSe confirmed by optical properties, reflectance data and chemical analyses. Experimental: The ternary system Pd-Sb-Se has not been studied yet. Our preliminary experimental results of on-going research have shown that milotaite forms stable association with palladseite (Pd17Se15) and antimonselite (Sb2Se3), and coexists with stibiopalladinite (Pd5Sb2) at 400 C.

10.5.15 NALDRETTITE PD2SB Crystallography: orthorhombic, Cmc21 ˚ , V 414.097 A ˚ 3, Z 5 8 Unit cell: a 3.3906, b 17.5551, c 6.957 A ˚ (I)(hkl)]: 2.2454(100)(132), 2.0567(52) X-ray powder diffraction pattern, strongest lines [d in A (043), 2.0009(40)(152), 1.2842(42)(115), 1.2122(50)(204), 0.8584(56)(1174), ICDD PDF2 card— 00-058-0460. Structure: isostructural with Pd2As Appearance: Occurs as anhedral grains (varying in size from 10 to 239 μm), commonly attached or molded to sulfide minerals, also associated with clinochlor, rarely with magnetite. Optical properties: In reflected light, bright creamy white, weak bireflectance, no pleochroism, distinct anisotropy (rotation tints deep bright blue, lemon-buff, and mauve pale pink); higher reflectance and less yellow against pentladite. Reflectance, [λnm, R1 R2 %]

470 546 589 650

air 49.0 50.9 53.2 55.1 55.4 57.5 58.5 60.1

im 35.9 37.6 40.3 42.1 42.5 44.3 45.4 47.2

Physical Properties: Opaque, metallic, irregular fracture. Hardness: VHN50 393 (358
418) g/mm2, Mohs 4-5 Cleavage: not observed Density: 10.694 g/cm3 (calc.) Chemical Composition (EMPA data, wt.%): P Pd 63.49, Fe 0.11, Sb 35.75, As 0.31, S 0.02 99.68 (Pd1.995Fe0.007)P2.002 P (Sb0.982As0.014S0.002) 0.998 P (n 5 69) Pd 63.61, Sb 36.39 100.00 Pd2Sb—ideal Type locality and occurrence: The Mesamax Northwest deposit, Ungava region, Queb´ec, Canada. It was also observed in the Tootoo and Mequillon magmatic sulfide deposits, New Quebec Orogen (Liu et al., 2013) and in concentrates of chromitite from the Korydallos area in the Pindos ophiolite complex, NW Greece (Kapsiotis et al., 2010). Observed as an unnamed phase in Cu-Ni sulfide deposits in clinopyroxenite intruding Permian sandy shales and volcanics, NE China and in a serpentinite intrusion in Permian metamorphic rocks, SW China (Cabri, 1981b, UN1974-8), in PGE mineralization in the Alaskan-type intrusive complexes near Fifield, New South Wales, Australia (Johan et al., 1989), in the vein-type Cu-Ni sulfide ores of the Ioko-Dovyren massif, northern Baikal region, Russia (Rudashevsky et al., 2003), and in Noril’sk ores (unpubl. data).

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339

Name: For Anthony J. Naldrett (b. 1933), professor at the University of Toronto, in recognition of his significant contributions to understanding the genesis of PGE deposits. Reference: Cabri et al. (2005), IMA No. 2004-007 Experimental: The mineral has a synthetic analogue synthesized by Ba¨lz and Schubert (1969), ICDD PDF2 01-074-6150 card, El-Boragy and Schubert (1971b) and Kim and Chao (1996). It melts incongruently at 580 C (Kim and Chao, 1996); below this temperature it coexists with Pd5Sb2 or PdSb.

10.5.16 NIELSENITE PDCU3 Crystallography: Tetragonal, P4mm ˚ , V 353.2 A ˚ 3, Z 5 4 Unit cell: a 3.7125, c 25.62 A ˚ (I)(hkl)]: 2.137(100)(117), 1.8596(70) X-ray powder diffraction pattern, strongest lines [d in A (200), 1.8337(40)(0014), 1.3126(60)(220), 1.1188(55)(317), 1.0663(30)(2214), ICDD PDF2 Structure: considered to be isostructural with synthetic tetragonal PdCu3, space group P4mm, but may belong to the P4/mmm group Appearance: Occurs as discrete grains or in sulfide-bearing, droplet-shaped to irregular grains 5
50 μm in size. Optical properties: In reflected light, bright creamy white, anisotropy not observed (due to grain orientation, parallel to c) Reflectance, [λnm, R0 %]

470 546 589 650

air 57.6 60.85 62.8 66.7

im 47.5 50.8 53.0 57.5

Physical Properties: Steel-gray with a metallic luster, black streak, sectile tenacity Hardness: not measured Cleavage: not observed Density: 9.53 g/cm3 (calc.) Chemical Composition (EMPA data, wt.%): P Pd 29.86, Pt 3.08, Au 3.70, Cu 61.96, Fe 0.59, Pb 0.17 99.36 (Pd0.862Au0.058Pt0.049Fe0.028 P Pb0.003)P1.00(Cu2.996Fe0.004 P ) 3.00(n511) Pd 35.82, Cu 64.18 100.00 PdCu3—ideal Type locality and occurrence: The Skaergaard intrusion, Kangerdlugssuaq area, Est Greenland (68 090 55v N, 31 410 02v W). Also, found in concentrates of chromitite from the Korydallos area in the Pindos ophiolite complex, NW Greece (Kapsiotis et al., 2010), in magnetite-bearing gabbroic rocks of the Freetown Layered Complex, Sierra Leone (Bowles et al., 2013) and in Au-Cu-Pd-type mineralization in dolerites from Alexandra Land Island of the Franz Josef Archipelago (Sklyarov et al., 2016). Name: After Troels F.D. Nielsen (b. 1950), a geologist with the Geological Survey of Denmark and Greenland, in recognition of his field work in the Skaergaard intrusion and his mineralogical and metallurgical studies.

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Reference: McDonald et al. (2008), IMA No.2004-046 Experimental: According to the study of Karup-Møller et al. (2008) the formation of the phase can be assumed to be a product of low-temperature re-equilibration, shown as a 1D-LPS (onedimensional long-period superlattice LPS) phase in the Cu-Pd phase diagram formed below 500 C (Subramanian and Laughlin, 1991).

10.5.17 NORILSKITE (PD,AG)7PB4 Crystallography: trigonal, P3121 ˚ , V 1202.92 A ˚ 3, Z 5 6 Unit cell: a 8.9656, c 17.2801 A ˚ (I)(hkl)]: 3.2201(29)(023,203), 2.3130 X-ray powder diffraction pattern, strongest lines [d in A (91)(026,206), 2.2414(100)(220), 1.6098(28)(046,406), 1.3076(38)(246,462), 1.2942(18)(600), 1.2115(37)(2212,1213), 0.9626(44)(0612,6012). Structure: Crystallizes in the Ni13Ga3Ge6 structure type, related to nickeline. The crystal structure was solved and refined from the powder X-ray-diffraction data of synthetic (Pd,Ag)7Pb4. Appearance: Forms anhedral grains in aggregates (up to about 400 μm) with polarite, zvyagintsevite, Pd-rich tetra-auricupride, Pd-Pt bearing auricupride, Ag-Au alloys, (Pb,As,Sb) bearing atokite, mayakite, Bi-Pb rich kotulskite and sperrylite in pentlandite, cubanite, and talnakhite. Optical properties: In reflected light, orange-brownish pink, moderate to strong bireflectance, orange-pink to greyish-pink pleochroism, strong anisotropy (rotation tints from dull yellow to dull blue in partially crossed polars); no internal reflections. Reflectance, [λnm, Ro Re0 %]

470 546 589 650

51.1 56.8 59.9 64.7

48.8 52.2 53.5 55.5

Physical Properties: Gray with metallic luster and gray streak, brittle. Hardness: VHN20 310 (296
342) g/mm2, Mohs 4 Cleavage: not observed Density: 12.99 g/cm3 (calc.) Chemical Composition (EMPA data,P wt.%): Pd 44.33, Ag 2.68, Bi 0.33, Pb 52.34 99.68 (Pd6.56Ag0.39)P6.97(Pb3.97Bi0.03)P4.00 (n 5 16) P Pd 42.95, Ag 3.87, Pb 53.51 P100.33 (Pd6.25Ag0.56)P6.81Pb4.00 (synth., n 5 8) Pd 43.93, Ag 3.43, Pb 52.64 100.00 (Pd6.5Ag0.5)P7Pb4—ideal based on crystal structure Type locality and occurrence: The Mayak mine of the Talnakh deposit, Russia (69 300 20v N,  88 270 17v E). Also observed from the Komsomolsky mine of the Talnakh deposit and from the Zapolyarny (Trans-Polar) mine of the Norilsk I deposit (Sluzhenikin and Mokhov, 2015). Name: For the Norilsk district, Russia. Almost half of all known named platinum-group minerals have been reported to occur in the Norilsk ores. Reference: Vymazalov´a et al. (2017), IMA No 2015-008 Note: The structural identity between the natural and synthetic (Pd,Ag)7Pb4 was confirmed by electron back-scattering diffraction (EBSD).

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341

Experimental: The phase was synthesized at 300 C. The system Pd-Ag-Pb was experimentally studied by Sarah et al. (1981) at 400 C. Based on the proposed phase diagram, norilskite forms a stable assemblage with zvyagintsevite (Pd3Pb) and Pd-Ag alloy, and coexists with Pd-Pb phases Pd5Pb3, Pd13Pb9, and PdPb.

10.5.18 PALLADOSILICIDE PD2SI Crystallography: hexagonal, P62m ˚ , V 125.5 A ˚ 3, Z 5 3 Unit cell: a 6.496, c 3.433 A ˚ (I)(hkl)]: 2.3658(100)(111), 2.1263(37) X-ray powder diffraction pattern, strongest lines [d in A (120), 2.1808(34)(021), 3.240(20)(110), 1.8752(19)030), 1.7265(12)(002), 1.3403(11)(122), 1.2089 (10)(231) (synth.) Structure: Fe2P type Appearance: Found in a heavy-mineral concentrate, grains ranging in size from 0.7 to 39.1 μm. Optical properties: In reflected light bright creamy white, weak bireflectance, weak anisotropy (rotation tints in shades of light blue and olive green) Reflectance, [λnm, R1 R2 %]

470 546 589 650

air 49.6 52.7 51.2 53.8 51.6 53.7 51.7 53.3

im. 36.3 37.6 37.8 37.9

38.6 39.5 39.5 39.3

Physical Properties: Has an anhedral to subhedral habit, metallic luster. Hardness: not measured Cleavage: not observed Density: 9.562-9.753 g/cm3 (calc.) Chemical Composition (EMPA data, wt.%): Si 7.95, Pd P 68.56, Ag 1.07, Ni 4.59, Te 0.32 Sb 0.36, As 3.95, Fe 0.64, Pt 1.72, Sn 1.79, Cu 2.18, Rh 2.39 95.53 (Pd1.657Ni0.201Cu0.088Rh0.06Fe0.029Ag0.026Pt0.023Sn0.039)P2.123(Si0.728As0.136 Sb0.008Te0.006)P0.878 (n 5 8)—Kapalagulu Si P 10.13, Pd 68.77, Ag 0.33, Ni 5.16, Sb 0.11, As 2.18, Fe 0.35, Pt 4.45, Sn 3.08, Cu 1.62, Rh 3.76 99.94 (Pd1.557Ni0.212Cu0.061Rh0.088Fe0.015Ag0.007Pt0.055Sn0.063)P2.058(Si0.869As0.07Sb0.002)P0.941 (n 512)—UG-2 P Pd 88.34 Si 11.66 100.00 Pd2Si—ideal Type locality and occurrence: PGE-chromite horizon of the Kapalagulu Intrusion near eastern shore of Lake Tanganyika, western Tanzania (30 030 51v E, 5 530 16v S and 30 050 37v E, 5 540 26v S) and the UG-2 chromitite, Bushveld Complex. Name: For the chemical composition: Pd, Si. Reference: Cabri et al. (2015), IMA No. 2014-080 Note: The structural identity of natural and synthetic Pd2Si (Nylund, 1966) was confirmed by electron back-scattering diffraction (EBSD). Experimental: The synthetic analogue melts congruently at 1330 C. Langer and Wachtel (1981) also observed a metastable state in the system, depending on the rate of cooling.

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ˇ 10.5.19 PASAVAITE PD3PB2TE2 Crystallography: orthorhombic, Pmmn ˚ , V 322.6 A ˚ 3, Z 5 2. Unit cell: a 8.599, b 5.9381, c 6.3173 A ˚ (I)(hkl)]: 6.3152(34)(001), 3.1572(33) X-ray powder diffraction pattern, strongest lines [d in A (002), 3.0495(100)(211), 2.5456(63)(202), 2.4424(34)(220), 2.2786(42)(221), 2.1637(71)(022), 2.1496(30)(400), 1.8906(42)(203), 1.5248(31)(422), ICDD PDF2 card—01-077-9121, synth. Structure: Solved and refined from the powder X-ray diffraction data of syntetic Pd3Pb2Te2. Structurally related to shandite (Ni3Pb2S2) and parkerite (Ni3Bi2S2). Appearance: Occurs as subhedral grains (less than 20 μm in diameter) embedded in polarite, randomly accompanied by Pd-Pb-Bi-Te phases, sperrylite or intergrown with Au-Ag phases. Optical properties: In reflected light, pale pink with brownish tinge, strong bireflectance, pleochroic from brownish to light pink, anisotropy distinct to strong, exhibits no internal reflections. Reflectance, [λnm, R1 R2 %]

470 546 589 650

nat. 42.4 44.6 45.7 46.9

synth. 49.9 51.8 52.2 52.8

Physical Properties: Opaque, gray with metallic luster and gray streak, brittle (synth.). Hardness: VHN25 233 (173
281), Mohs 2 Cleavage: {001} weak Density: 10.18 g/cm3 (calc.), 9.9 g/cm3 (meas. on synth.) Chemical Composition (EMPA data, wt.%): P Pd 31.51, Pb 41.54, Bi 0.19, Te P25.75 98.99 Pd2.96(Pb2.01Bi0.01)Te2.02 (n 5 4) Pd 32.17, Pb 41.78, Te 25.93 P99.88 Pd2.99Pb2.00Te2.01 (synth., n 5 7) Pd 32.28, Pb 41.91, Te 25.81 100.00 Pd3Pb2Te2—ideal Type locality and occurrence: The Talnakh deposit, Norilsk-Talnakh Ni-Cu camp, Taimyr Autonomous District, Russia. Name: For Jan Paˇsava (b. 1957) of the Czech Geological Survey, in recognition of his contributions to the mineralogy and geochemistry of PGE in anoxic environments and other related ore deposits. Reference: Vymazalov´a et al. (2009), IMA No 2007-059 Note: The structural identity of natural and synthetic Pd3Pb2Te2 was confirmed by electron back-scattering diffraction (EBSD). Experimental: Phase relations in the system Pd-Pb-Te were determined at 400 C (Vymazalov´a and Dr´abek, 2011); the Pd-rich corner at 480 C was explored by El-Boragy and Schubert (1971b). At 400 C the system contains two ternary compounds: paˇsavaite and Pd71Pb8Te21 (not known to occur in nature). Paˇsavaite forms a stable assemblage with kotulskite solid-solution (25
30 at.% Pb) and altaite (PbTe). Paˇsavaite melts at 500 C.

10.5.20 SKAERGAARDITE PDCU Crystallography: cubic, Pm3m ˚ , V 27.0378 A ˚ 3, Z 5 1 Unit cell: a 3.0014 A

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343

˚ (I)(hkl)]: 2.122(100)(110), 1.5000(20) X-ray powder diffraction pattern, strongest lines [d in A (200), 1.2254(20)(211), 0.9491(20)(310), 0.8666(10)(222), 0.8021(70)(321), ICDD PDF2 card—00057-0606. Structure: CsCl-type. Isostructural with wairauite (CoFe), synthetic CuZn (β-brass) and structuraly related to hongshiite (PtCu). Appearance: Occurs as droplets, equant grains with rounded outlines, subhedral to euhedral crystals and irregular grains, in size from 2 to 75 μm. Optical properties: In reflected light, bright creamy white (against to bornite and chalcopyrite), bright white (against digenite and chalcocite), isotropic. Reflectance, [λnm, R1 R2 %]

470 546 589 650

air 58.65 62.6 64.1 65.25

im. 47.4 51.1 52.8 53.95

Physical Properties: Steel gray with a bronze tint, metallic luster, sectile. Hardness: VHN25 257 (244
267) g/mm2, Mohs 4
5 Cleavage: not observed Density: 10.64 g/cm3 (calc.) Chemical Composition (EMPA data, wt.%): P Pd 58.94, Pt 1.12, Au 2.23, Cu 29.84, Fe 3.85, Zn 1.46, Sn 1.08, Te 0.28, Pb 0.39 99.19 P (Pd0.967Au0.020Pt0.010)PP 0.997(Cu0.820Fe0.120Zn0.039Sn0.016Te0.004Pb0.003) 1.002 (n 5311) Cu 37.39 Pd 62.61 100.00 CuPd—ideal Type locality and occurrence: The Skaergaard intrusion, Kangerdlugssuaq area, East Greenland. Also found in a heavy-mineral concentrate from the Marathon deposit, Coldwell Complex, Canada (McDonald et al., 2015). Observed in concentrates of chromitite from the Korydallos area in the Pindos ophiolite complex, NW Greece (Kapsiotis et al., 2010); in Au-CuPd-type mineralization in dolerites from Alexandra Land Island of the Franz Josef Archipelago (Sklyarov et al., 2016); in PGE mineralization in the Kirakkajuppura PGE deposit, Penikat layered complex, Finland (Barkov et al., 2005), and from the J-M reef, Stillwater Complex (Godel and Barnes, 2008). Name: For the Skaergaard intrusion in East Greenland. Reference: Rudashevsky et al. (2004), IMA No. 2003-049 Experimental: The transformation from disordered (Cu,Pd) solid solution to ordered CuPd occurs over the range 35
50 at.% Pd at 596 C (Subramanian and Laughlin, 1991).

10.5.21 TO¨RNROOSITE PD11AS2TE2 Crystallography: cubic, Fd3m ˚ 3, Z 5 8 Unit cell: a 12.3530, V 1885.03 A ˚ (I)(hkl)]: 2.182(100)(440), 2.376(90) X-ray powder diffraction pattern, strongest lines [d in A (511,333), 1.544(15)(800), 1.862(13)(622), 1.2606(13)(844), 1.608(11)(731,553) Structure: Isostructural with isomertierite (Pd11As2Sb2) and miessiite (Pd11Se2Te2).

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CHAPTER 10 EXPERIMENTAL ASPECTS OF PLATINUM-GROUP MINERALS

Appearance: Observed as an anhedral grain (size 132 x 200 μm), discovered with placer gold and PGM nuggets. Optical properties: In reflected light yellowish white, isotropic. Reflectance, [λnm, R%]

470 546 589 650

45.4 51.0 54.1 57.45

Physical Properties: Black, opaque with metallic luster, silvery black streak, malleable. Hardness: VHN25 519 (509
536) kg/mm2, Mohs 5. Cleavage: not reported Density: 11.205 g/cm3 (calc.) Chemical Composition (EMPA data, wt.%): P Pd 72.04, Pt 1.75, Sb 2.13, Sb 0.85, As 8.77, Te 13.15, Bi 0.79 99.48 (Pd10.85Pt0.14)P10.99 P (As1.88Sb0.11)P1.99(Te1.65Sn0.29BiP 0.06) 2.00 (n 5 10) Pd 72.29, As 9.51, Te 16.20 100.00 Pd11As2Te2—ideal Type locality and occurrence: The Miessijoki River, Lemmenjoki area, Inari Commune, Finnish Lapland, Finland (25 420 33v N, 68 420 30v E). Also observed in a heavy-mineral concentrate from the Marathon Cu-PGE-Au deposit, Coldwell Complex, Ontario, Canada (McDonald et al., 2015) and in the sulfide-bearing pegmatoidal pyroxenites of the South Sopcha intrusion of the Monchegorsk Igneous Complex, Kola peninsula, Russia (Grokhovskaya et al., 2012), in PGE mineralization of the Fedorova-Pana ore node (Subbotin et al., 2012) and as an unnamed phase in PGE concentrate from alluvial sediments from the farm Maandagshoek in the eastern Bushveld (Oberthu¨r et al., 2004). Name: For Ragnar To¨rnroos (b. 1943), University of Helsinki, for his pioneering research on placer PGM in Finnish Lapland and his contributions to ore mineralogy. Reference: Kojonen et al. (2011), IMA No 2010-043 Note: The crystal structure of to¨rnroosite was refined on a single crystal sample from the South Sopcha intrusion, Russia by Karimova et al. (2016), the data are in an agreement with those proposed by Kojonen et al. (2011). Experimental: The synthetic analogue is not known. The system Pd-As-Te was experimentally studied by El-Boragy and Schubert (1971b) at 480 C, but it requires some further re-examination, particularly in the Pd-rich corner, reflecting new observations in the binary systems Pd-Te and PdAs. The phase assigned as Pd6AsTe by El-Boragy and Schubert (1971b) could be in fact Pd11As2Te2.

10.5.22 UNGAVAITE PD4SB3 Crystallography: tetragonal, P41212, P4122, P43212, P42212 or P4222 ˚ , V 1446.02 A ˚ 3, Z 5 8 Unit cell: a 7.7388, c 24.145 A ˚ (I)(hkl)]: 3.008(90)(008), 2.268(100) X-ray powder diffraction pattern, strongest lines [d in A (134), 2.147(30)(230), 1.9404(60)(400), 1.2043(30)(2218,452), 1.2002(30)(624), ICDD PDF2 card—00-058-0505.

10.5 PLATINUM-GROUP MINERALS AND SYNTHETIC ANALOGUES

345

Structure: not determined Appearance: Occurs as rare anhedral grains with inclusions of Au-Ag alloy or with attached chalcopyrite and a chlorite-group mineral, from 36 to 116 μm in size. Optical properties: In reflected light, bright creamy white, weak bireflectance, no pleochroism, weak anisotropy (rotation tints pale blue-gray to deep blue). Reflectance, [λnm, R1 R2 %]

470 546 589 650

air 50.2 50.5 55.6 55.9 57.9 58.3 60.2 60.7

im. 37.6 43.2 45.9 48.1

38.0 43.5 46.3 48.5

Physical Properties: Opaque, dark gray, metallic, malleable. Hardness: not measured Cleavage: not observed Density: 7.264 g/cm3 (calc.) Chemical Composition (EMPA data, wt.%): P Pd 54.53, Fe 0.13, Te 0.09, Sb 44.59, Bi 0.42 Hg 0.19 As 0.20 100.15 P Pd4.062(Sb2.893Fe0.017BiP 0.017Hg0.006Te0.005) 2.938 (n 5 16) Pd 53.82 Sb 46.18 100.00 Pd4Sb3—ideal Type locality and occurrence: The Mesamax Northwest Ni-Cu-Co-PGE deposit in the Cape Smith fold belt of the Ungava region, northern Quebec, Canada (61 340 25v N, 73 150 36v W). Also observed in the Tootoo and Mequillon magmatic sulfide deposits, New Quebec Orogen (Liu et al., 2013). Name: After the locality in the Ungava region, Quebec, Canada. Reference: McDonald et al. (2005), IMA No. 2004
020 Note: Some further experimental and crystal structure investigations are needed. Experimental: The synthetic analogue is not known from the experimental studies related to Pd-Sb system (El-Boragy and Schubert, 1971b), nor from studies on ternary systems involving Pd and Sb including those made by Kim and Chao (1991, 1996), Cabri et al. (1975).

10.5.23 ZACCARINIITE RHNIAS Crystallography: tetragonal, P4/nmm ˚ , V 77.59 A ˚ 3, Z 5 2 Unit cell: a 3.5498, c 6.1573 A ˚ (I)(hkl)]: 2.5092(40)(110), 2.3252(100) X-ray powder diffraction pattern, strongest lines [d in A (111,102), 1.9453(51)(112), 1.7758(80)(103,200), 1.2555(40)(213,220), 1.1044(22)(302,311), 1.0547(23)(312), 0.9730(42)(215). (synth.) Structure: Cu2Sb type. The crystal structure was refined from the powder XRD data of synthetic RhNiAs using the initial structural model of Roy-Montreuil et al. (1984), ICSD card No187596. Appearance: Forms anhedral grains (1
20 μm in size), intergrown with garutiite, in association with hexaferrum, Ru-Os-Ir-Fe alloys, and Ru-Os-Ir-Fe oxygenated compounds in chromite. Optical properties: In reflected light, white with brownish to pinkish tints, has moderate to strong bireflectance, a strong white to pinkish brownish white pleochroism, strong anisotropy (with rotation tints from orange to blue-green); exhibits no internal reflections.

346

CHAPTER 10 EXPERIMENTAL ASPECTS OF PLATINUM-GROUP MINERALS

Reflectance, [λnm, R1 R2 %]

470 546 589 650

nat. 49.4 52.6 52.4 53.2 54.2 53.2 56.6 53.3

synth. 49.1 53.1 55.2 57.9

53.3 54.1 53.9 53.9

Physical Properties: Opaque, metallic luster, gray streak, brittle. Hardness: VHN5 218 (166
286) g/mm2, Mohs 31/2
4 Cleavage: not observed Density: 10.19 g/cm3 (calc.), 10.09 g/cm3 (meas. on synth.) Chemical Composition (EMPA data, wt.%): P Rh 41.77, Os 0.51, Ir 0.64, Ru 0.46, Pd 0.34, Ni 23.75, Fe 0.53, As 27.84, S 0.10, 96.09 wt. P P P %, (Rh1.01Os0.01Ir0.01Ru0.01Pd0.01)P (Ni Fe ) (As S ) 1.05 1.02 0.93(n53) 1.00 0.02 0.92 0.01 Rh 44.57, Ni 24.50, As 31.82 P100.88 Rh1.02Ni0.98As1.00 (synth., n 5 28) Rh 43.51, Ni 24.82, As 31.67 100.00 RhNiAs—ideal Type locality and occurrence: The Loma Peguera ophiolitic chromitite, Dominican Republic. It has been observed from several localities worldwide, e.g., the Guli chromitite, Ray-Iz ophiolite complex, Nizhny Tagil, the ophilitic belt in the Koryak-Kamchatska fold region in Russia, the Thetford Mines in Canada, the Vourinos complex in Greece, and the Bushveld complex in South Africa. Name: For Federica Zaccarini (b. 1962) of the University of Leoben, in recognition of her contributions to PGE mineralogy and related deposits. Reference: Vymazalov´a et al. (2012b), IMA No. 2011-086 Note: The structural identity between the natural and synthetic RhNiAs was confirmed by Raman spectroscopy. Experimental: The phase was synthesized at 800 C; the system Rh-As-Ni has not been experimentally investigated.

ACKNOWLEDGEMENTS We are very grateful to Louis J. Cabri and Emil Makovicky for their detailed and helpful comments on the manuscript. We are grateful to Sisir K. Mondal and William L. Griffin for the editorial handling and for reading the final manuscript and correcting the English.

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